© 2019, Brazilian Association of Computational Mechanics. All rights reserved.This work presents an analysis of an ocean wave energy harvesting system. This system is composed of a direct current (DC) power generator attached at the middle-top of a floating platform. A pendulum is connected to the generator’s shaft. It is considered that the ocean waves motion swings the platform in the vertical direction, which transfers energy to the pendulum, making possible to convert mechanical energy, induced by the ocean wave, into a rotational motion due the pendulum and after in electric energy due the generator. With the objective to optimize the harvested power, several analyses of the pendulum parameters, ocean wave amplitude and frequency were carried out. This work was based on the Brazilian’s coast characteristics. Numerical and experimental results were performed which shows the efficiency of the conversion of mechanical energy provided by the pendulum into electric power.

© 2019, Brazilian Association of Computational Mechanics. All rights reserved.In this paper a mathematical model was found, and numerical results obtained for the pendulum behavior when coupled to a DC generator. A simple pendulum is vertically excited on its support and consequently exhibiting oscillations and rotations. The motion of the pendulum spins the axis of a DC generator and inducing a current. The dynamic model involving the generator and the pendulum dynamics is developed and analyzed in this article. Bifurcation diagrams demonstrate doubling-period and saddle-node bifurcations with the chaos. The presence of chaos is verified by the Lyapunov exponents applied on the time series of the pendulum speed and position. Nonideal interactions of a DC motor with a pendulum by a crank-shaft-slider mechanism is analyzed and compared with an ideal excitation of the pendulum.

© 2019 Praise Worthy Prize S.r.l.-All rights reserved.– The addition of an anti-roll bar for the dynamics of a full-car has improved the safety and comfort of the passengers along the years. For lorries and buses, the anti-roll bar is a standard configuration with active suspension, and it is heavily used when at high-speed on bumpy roads or tight bends. The adoption of the anti-roll bar corrects the undesired behavior and softens the suspension improving the comfort, and the active bar guarantees a safety operation. However, its adoption on cars depends on the category and the expected road. In this paper, the difference between front and rear anti-roll bars with a Magnetorheological (MR) damper to improve safety on regular cars is investigated. A square wave is used as a burst along ten seconds to compare and contrast the efficiency of the system with front and rear bar combined and separated. The MR damper was added with SDRE (State Dependent Riccati Equation) control to provide an extra safety level. The numerical results show that the impact of a nonlinear anti-roll bar on the rear affects the stability. The influence of lag angles led to a more active control.

© 2019, The Society for Experimental Mechanics, Inc.The influence of the aircraft boundary conditions when setting a Ground Vibration test is always an issue. As aircrafts designs are becoming bigger is size and weight, the challenge in developing test set-ups for a successful GVT also increases. These challenges include not only the mechanical design of test devices, but also the goal to have the test performed in a shorter time, and with limited budget. Embraer decided years ago to have reliable device, which could duplicate the aircraft boundary condition, allowing at the same time fast test set-up and fast dismount. Even though, that design was modified and some opportunities had to be evaluated. This paper shows the conclusions of some variations on actual aircraft GVT set-ups, as well as studies performed in a small aircraft- like structure.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering.The residual stresses generated during the deep rolling process made on crankshafts are still not fully understood to this day. Comprehending and correctly simulating the process dynamics are key to investigate the process influence over the material microstructure. A numerical model using an explicit formulation was developed in order to accurately simulate deep rolling dynamics. Real boundary conditions, contact and a converged mesh were set. Diverse mass scaling and load rate were tested for comparison. The results were evaluated in terms of the simulation energy balance, as the internal, kinetic and artificial energies outputs were confronted. Conclusions could be inferred on the accuracy of the model representation of the real process based on this analysis.

© 2018 Elsevier B.V.TWIP steel weld spots were produced by varying the following welding parameters: welding current, welding time and electrode clamping force. Hardness distributions along the weld spots cross section were obtained by Vickers microindentations. The mechanical strength and failure modes of the weld spots were assessed by tensile-shear tests. Weibull statistics was applied to statistically analyse the data from tensile-shear loading. The results highlighted the influence of welding parameters variations on the Vickers hardness and residual stress state. These properties have a positive correlation to the failure modes and so the mechanical reliability of the weld spots. Welds that failed in pullout mode and partial-interfacial failure mode have statistically higher load bearing capacity than those in interfacial failure mode. The combination of a welding current of 8 kA with a welding time of 16 cycles and an electrode clamping force of 2 kN showed to be the optimum parameters for the investigated TWIP steel weld spots. By using this optimum setup, it was possible to supress interfacial failure mode and to obtain pullout as the predominant failure mode, considerably increasing the mechanical reliability of the weld spots.

© 2019 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Aircraft with three engines, as known as trijet, became a standard design among manufacturers after 1964 when the FAA’s 60-minute rule was exempted for these aircraft. This regulation restricted the flight path to 60 minutes’ flying time to a suitable airport, therefore affecting the operation costs and limiting the range of twin-jet aircraft. However, improvements to the engine’s reliability in the following decades allowed ETOPS certification for twinjet aircraft. The traditional trijet designs were slowly retired, the last commercial trijet flight was in 2014.The industry abandoned the design as solution for commercial aviation; however, executive jets such as the Falcon 7x and Falcon 8x, certified in 2016, show that this configuration might still be advantageous for specific markets. The certification at one engine inoperative condition presents an advantage for trijet aircraft, reducing takeoff thrust, since when one engine is inoperative, 67% of the total thrust is available for the trijet aircraft, while this value is only 50% for a twin-jet aircraft. The aircraft design is related to a multidisciplinary view. So, the thrust reduction and the implementation of a third engine have impacts on fuel burn, structural weight, external noise, performance, certification, maintenance, and the fuel feed system. In this sense, the multidisciplinary view justifies distinct thrust to weight ratio reduction caused by trijet configuration for different MTOW range. The aim of this work was to study the viability of a trijet aircraft configuration and potential advantages for a regional aviation scenario. The trijet configuration performance was evaluated and compared to twinjet configuration in a multidisciplinary design environment considering disciplines such as aero-dynamics, noise, performance, flight mechanic, weight, and structure. In addition, it was also assessed potential benefits from boundary layer ingestion of the engine over the fuselage and APU removal, since electrical engine starting becomes more feasible for small engines, as in the trijet scenario. An aircraft with MTOW ranging from 10,580 to 545,000 lb. was studied and the results showed that a reduction up to 7.0% of installed thrust might be achieved with the trijet design compared to twin-jet aircraft when the field length defined by aviation regula-tions is the critical constraint. However, flyover noise, structural weight and direct operating cost might increase in trijet design. In this sense, a correlation between twin-jet MTOW and trijet DOC was developed in order to aid early aircraft design decisions between both design configurations.

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimIn the present work, the Pt(111) surface was disordered by controlling the density of {110}- and {100}-type defects. The cyclic voltammogram (CV) of a disordered surface in acid media consists of three contributions within the hydrogen adsorption/desorption region: one from the well-ordered Pt(111) symmetry and the other two transformed from the {111}-symmetry with contributions of {110}- and {100}-type surface defects. The ethanol oxidation reaction (EOR) was studied on these disordered surfaces. Electrochemical studies were performed in 0.1 M HClO4+0.1 M ethanol using cyclic voltammetry and chronoamperometry. Changes in current densities associated to the specific potentials at which each oxidation peak appears suggest that different surface domains of disordered platinum oxidize ethanol independently. Additionally, as the surface-defect density increases, the EOR is catalysed better. This tendency is directly observed from the CV parameters because the onset and peak potentials are shifted to less positive values and accompanied by increases in the oxidation-peak current on disordered surfaces. Similarly, the CO oxidation striping confirmed this same tendency. Chronoamperometric experiments showed two opposite behaviors at short oxidation times (0.1 s). The EOR was quickly catalyzed on the most disordered surface, Pt(111)-16, and was then rapidly deactivated. These results provide fundamental information on the EOR, which contributes to the atomic-level understanding of real catalysts.

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. This work investigates the influence of different nitration protocols of a carbon black, the addition of tungsten carbide (WC), and the presence of iron, in terms of the catalytic activity of electrocatalysts containing Fe-N x moieties towards the oxygen reduction reaction (ORR) in acidic and alkaline media. The synthesized materials were characterized using X-ray diffraction (XRD), Raman spectroscopy (Raman), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) with a rotating ring-disk electrode (RRDE), in addition to durability tests. In acidic media, the performance of the catalysts varied according to the type of nitration protocol, the presence of iron, and the heat treatment temperature, which is accompanied by variations in the ORR mechanism. In alkaline electrolyte, the electrocatalysts presented higher performances, with only an ~0.04-V difference relative to that of a standard platinum on carbon catalyst. The number of electrons transferred per oxygen molecule, the amounts of hydrogen peroxide generated in the ORR, the effect of catalyst loading, and the presence of iron in the catalysts were investigated with the aim of understanding the ORR mechanism and assisting in the production of high-performance and durable materials. Finally, the two best electrocatalysts were submitted to a standard durability test, which evidenced promising high stability at both pHs. [Figure not available: see fulltext.].

© 2019 American Chemical Society. In this work, a detailed kinetic analysis of the oxygen reduction reaction (ORR) on platinum is performed by applying steady and non-steady-state methodologies at stationary and rotating disk electrodes and by comparing experimental results to calculated curves via digital simulations. Results reveal the existence of a complex chemical-electrochemical-chemical-electrochemical initial reaction sequence, a CECE-mechanism, and the possible contribution of a parallel disproportionation process in acid media during the reaction. Under convection-controlled circumstances, the first charge-transfer step would be the rate-determining step (RDS) on bulk electrodes, in agreement with early reports, but at different working conditions other initial steps can become the RDS. Additionally, contrary to the current accepted view, results support the formation of a soluble intermediate in the initial, and fast, chemical reaction, with a short lifetime, compatible with the formation of either the hydroperoxyl radical, HO 2 ∗, or superoxide anion, O 2 - , followed by a fast protonation. In light of present results, possible mechanisms, including the oxidation of H 2 O 2 that could be produced either by disproportionation or by reduction of HO 2 ∗, and/or O 2 - , radicals, are discussed. This interrelated reaction scheme would be the principal cause of large ORR overpotentials, but at the same time, it would open the opportunity for designing alternative catalysts beyond fundamental limits imposed by the apparent scaling relations between reaction intermediates, such as OH ads , O ads , and HO 2,ads adsorbates.

© 2019 Acoustical Society of America.An investigation of a wavepacket model for free-jet and jet-surface interaction noise was conducted. The source term for the axisymmetric mode was extracted from a Mach 0.9 jet large eddy simulation and employed to adjust the parameters of a simple source model. Streamwise coherence decay, in particular, was considered. The source model was propagated with both the free-field and tailored Green's function for a semi-infinite flat plate positioned at a distance of r/D = 1 from the jet axis. Significant deviations were observed in the prediction of the low-Angle directivity of the isolated jet as well as in the reproduction of the characteristics of the source field. However, the effects of trailing edge noise were well reproduced. The installed jet case, at the region dominated by trailing-edge scattering, showed very little sensitivity to the coherence decay, a crucial feature in the isolated jet case. In this sense, the modelling of the installed-jet case proved to be much simpler.

© 2019 Cambridge University Press.The linear stability of high-Reynolds-number corrugated jets is investigated by solving the compressible Rayleigh equation linearized about the time-averaged flow field. A Floquet ansatz is used to account for periodicity of this base flow in the azimuthal direction. The origin of multiple unstable solutions, which are known to appear in these non-circular configurations, is traced through gradual perturbations of a parametrized base-flow profile. It is shown that all unstable modes are corrugated jet continuations of the classical Kelvin-Helmholtz modes of circular jets, highlighting that the same instability mechanism, modified by corrugations, leads to the growth of disturbances in such flows. It is found that under certain conditions the eigenvalues may form saddles in the complex plane and display axis switching in their eigenfunctions. A parametric study is also conducted to understand how penetration and number of corrugations impact stability. The effect of these geometric properties on growth rates and phase speeds of the multiple unstable modes is explored, and the results provide guidelines for the development of nozzle configurations that more effectively modify the Kelvin-Helmholtz instability.

© 2019 American Physical Society.A large-eddy simulation of turbulent, compressible flow around a NACA 0012 airfoil at zero angle of attack and Mach number 0.115 is used to study mechanisms of trailing-edge noise. The boundary layers at both sides of the airfoil have a forced transition near the airfoil leading edge, and are turbulent near the trailing-edge. Flow-acoustic correlations and spectral (frequency-domain) proper orthogonal decomposition (SPOD) are used to evaluate turbulent structures that are relevant for the radiated sound. Homogeneity in the spanwise direction allows application of a Fourier decomposition in span prior to both correlations and SPOD. It is known that acoustic theory, based on an analysis of the tailored Green's function modeling trailing-edge scattering, shows that only spanwise wave numbers kz satisfying kz<k, where k is the acoustic wave number, lead to radiated sound; two-dimensional disturbances (kz=0) always satisfy this criterion, and thus spanwise-coherent structures are expected to be important for trailing-edge noise. Analysis of turbulence statistics of the boundary layer close to the trailing edge shows that the well-known, dominant streaky structures have kz>k and thus should not contribute to the radiated sound. To investigate this further using simulation data, flow-acoustic correlations are obtained using either the standard two-point analysis or considering two-dimensional disturbances in velocity and pressure fields, and results show significant correlation coefficients (of about 0.5) once two-dimensional disturbances near the trailing edge are isolated. A further increase of correlation peaks (up to 0.7) is obtained once the antisymmetric parts of the fields is considered, reflecting the classical antisymmetric nature of trailing-edge scattering. SPOD is then used for frequencies around the peak radiated sound to examine the structure of two-dimensional disturbances in the trailing-edge region and their contribution to radiated sound. Leading SPOD modes show coherent hydrodynamic waves propagating from the region of boundary-layer tripping toward the trailing edge, characterizing a noncompact source akin to wave packets seen in turbulent jets. These leading SPOD modes have significant contribution to the radiated sound, as two modes lead to 50% of the acoustic intensity for the lower studied frequencies. The present results point to the scattering of spanwise-coherent boundary-layer structures as the dominant mechanism of trailing-edge noise in this flow.

© 2019 Cambridge University Press.Streaks have been found to be an important part of wall-turbulence dynamics. In this paper, we extend the analysis for unbounded shear flows, in particular a Mach 0.4 round jet, using measurements taken using dual-plane, time-resolved, stereoscopic particle image velocimetry (PIV) taken at pairs of jet cross-sections, allowing the evaluation of the cross-spectral density of streamwise velocity fluctuations resolved into azimuthal Fourier modes. From the streamwise velocity results, two analyses are performed: the evaluation of wavenumber spectra (assuming Taylor's hypothesis for the streamwise coordinate) and a spectral proper orthogonal decomposition (SPOD) of the velocity field using PIV planes in several axial stations. The methods complement each other, leading to the conclusion that large-scale streaky structures are also present in turbulent jets where they experience large growth in the streamwise direction, energetic structures extending up to eight diameters from the nozzle exit. Leading SPOD modes highlight the large-scale, streaky shape of the structures, whose aspect ratio (streamwise over azimuthal length) is approximately 15. The data were further analysed using SPOD, resolvent and transient growth analyses, good agreement being observed between the models and the leading SPOD mode for the wavenumbers considered. The models also indicate that the lift-up mechanism is active in turbulent jets, with streamwise vortices leading to streaks. The results show that large-scale streaks are a relevant part of the jet dynamics.

© 2019 The Author(s) Published by the Royal Society. All rights reserved.This paper is focused on the study of a kinematic wavepacket model for jet noise based on two-point statistics. The model contains physical parameters that define its structure in terms of wavenumber, envelope shape and coherence decay. These parameters, which are necessary to estimate the sound pressure levels radiated by the source, were educed from a largeeddy simulation database of a Mach 0.4, fully turbulent jet. The sound pressure levels predicted by the model were compared with acoustic data and the results show that when the parameters are carefully educed from the data, the sound pressure levels generated are in good agreement with experimentally measured values for low Strouhal numbers and polar angles. Furthermore, here we show that a correct representation of both coherence decay and wavepacket envelope shape are key aspects to an accurate sound prediction. A Spectral Proper Orthogonal Decomposition (SPOD) of the model source was also performed motivated by the search for a low-rank model capable of capturing the acoustic efficiency of the full source. It is shown that only a few SPODmodes are necessary to recover acoustically important wavepacket traits.

© 2019 Acoustical Society of America.Acoustic measurements of turbulent jets in the vicinity of a flat plate, mimicking a neighbouring wing, were compared to results from two wavepacket-based source models previously studied in the literature: the Tailored Green's Function method, which considers the radiation of the turbulent structure in the vicinity of a semi-infinite flat plate, and the Boundary Element Method, which can represent the full geometry of the plate used in the experiments. Particular interest is given to analysing how the angle of attack of the plate (α) affects the sound radiated by an installed jet with trailing edge 6 diameters away from the nozzle and 1 diameter away from the centerline for 0° ≤ α ≤ 45°. The results herein confirm the behaviour identified by the models: the scattered acoustic field follows the rotation of the plate, shifting a silence region with negligible scattered sound, and creating regions with lower noise levels in positions that correspond to the ground for an aircraft with engines under its wings. This is further explored by means of a Mach number analysis for M = 0.5, 0.7, and 0.9, showing that this trend is present whenever trailing-edge scattering of jet disturbances is dominant in the acoustic field.

© 2019 American Physical Society.Coherent turbulent wave-packet structures in a jet at Reynolds number 460000 and Mach number 0.4 are extracted from experimental measurements and are modeled as linear fluctuations around the mean flow. The linear model is based on harmonic optimal forcing structures and their associated flow response at individual Strouhal numbers, obtained from analysis of the global linear resolvent operator. These forcing-response wave packets ("resolvent modes") are first discussed with regard to relevant physical mechanisms that provide energy gain of flow perturbations in the jet. Modal shear instability and the nonmodal Orr mechanism are identified as dominant elements, cleanly separated between the optimal and suboptimal forcing-response pairs. A theoretical development in the framework of spectral covariance dynamics then explicates the link between linear harmonic forcing-response structures and the cross-spectral density (CSD) of stochastic turbulent fluctuations. A low-rank model of the CSD at given Strouhal number is formulated from a truncated set of linear resolvent modes. Corresponding experimental CSD matrices are constructed from extensive two-point velocity measurements. Their eigenmodes (spectral proper orthogonal or SPOD modes) represent coherent wave-packet structures, and these are compared to their counterparts obtained from the linear model. Close agreement is demonstrated in the range of "preferred mode" Strouhal numbers, around a value of 0.4, between the leading coherent wave-packet structures as educed from the experiment and from the linear resolvent-based model.

© 2019 Cambridge University Press.Motivated by recent studies that have revealed the existence of trapped acoustic waves in subsonic jets (Towne et al., J. Fluid Mech., vol. 825, 2017, pp. 1113-1152), we undertake a more general exploration of the physics associated with acoustic modes in jets and wakes, using a double vortex-sheet model. These acoustic modes are associated with eigenvalues of the vortex-sheet dispersion relation; they are discrete modes, guided by the vortex sheet; they may be either propagative or evanescent; and under certain conditions they behave in the manner of acoustic-duct modes. By analysing these modes we show how jets and wakes may both behave as waveguides under certain conditions, emulating ducts with soft or hard walls, with the vortex-sheet impedance providing effective 'wall' conditions. We consider, in particular, the role that upstream-travelling acoustic modes play in the dispersion-relation saddle points that underpin the onset of absolute instability. The analysis illustrates how departure from duct-like behaviour is a necessary condition for absolute instability, and this provides a new perspective on the stabilising and destabilising effects of reverse flow, temperature ratio and compressibility; it also clarifies the differing symmetries of jet (symmetric) and wake (antisymmetric) instabilities. An energy balance, based on the vortex-sheet impedance, is used to determine stability conditions for the acoustic modes: these may become unstable in supersonic flow due to an energy influx through the shear layers. Finally, we construct the impulse response of flows with zero and finite shear-layer thickness. This allows us to show how the long-time wavepacket behaviour is indeed determined by interaction between Kelvin-Helmholtz and acoustic modes.

© 2019 Cambridge University Press.Three methods are evaluated to estimate the streamwise velocity fluctuations of a zero-pressure-gradient turbulent boundary layer of momentum-Thickness-based Reynolds number up to , using as input velocity fluctuations at different wall-normal positions. A system identification approach is considered where large-eddy simulation data are used to build single and multiple-input linear and nonlinear transfer functions. Such transfer functions are then treated as convolution kernels and may be used as models for the prediction of the fluctuations. Good agreement between predicted and reference data is observed when the streamwise velocity in the near-wall region is estimated from fluctuations in the outer region. Both the unsteady behaviour of the fluctuations and the spectral content of the data are properly predicted. It is shown that approximately 45Â % of the energy in the near-wall peak is linearly correlated with the outer-layer structures, for the reference case . These identified transfer functions allow insight into the causality between the different wall-normal locations in a turbulent boundary layer along with an estimation of the tilting angle of the large-scale structures. Differences in accuracy of the methods (single-and multiple-input linear and nonlinear) are assessed by evaluating the coherence of the structures between wall-normally separated positions. It is shown that the large-scale fluctuations are coherent between the outer and inner layers, by means of an interactions which strengthens with increasing Reynolds number, whereas the finer-scale fluctuations are only coherent within the near-wall region. This enables the possibility of considering the wall-shear stress as an input measurement, which would more easily allow the implementation of these methods in experimental applications. A parametric study was also performed by evaluating the effect of the Reynolds number, wall-normal positions and input quantities considered in the model. Since the methods vary in terms of their complexity for implementation, computational expense and accuracy, the technique of choice will depend on the application under consideration. We also assessed the possibility of designing and testing the models at different Reynolds numbers, where it is shown that the prediction of the near-wall peak from wall-shear-stress measurements is practically unaffected even for a one order of magnitude change in the corresponding Reynolds number of the design and test, indicating that the interaction between the near-wall peak fluctuations and the wall is approximately Reynolds-number independent. Furthermore, given the performance of such methods in the prediction of flow features in turbulent boundary layers, they have a good potential for implementation in experiments and realistic flow control applications, where the prediction of the near-wall peak led to correlations above 0.80 when wall-shear stress was used in a multiple-input or nonlinear scheme. Errors of the order of 20Â % were also observed in the determination of the near-wall spectral peak, depending on the employed method.

© The Author(s) 2018.In the present work, a numerical and experimental study of the thermoacoustic instabilities of a combustor is performed. The numerical model is represented by the one-dimensional linearised Euler Equation and an n-τ formulation for flame transfer function that describes the unsteady combustion response to these acoustic disturbances. This approach is similar to other simplified models present in the literature. However, most theoretical works assume a constant density and speed of sound in the medium, which is not realistic for combustion chambers, as the mean temperature is expected to decrease spatially as one moves away from the combustion area. Hence, to compare with experiments where chamber temperature is spatially varying, we developed a numerical solution procedure, seeking eigenvalues (complex-valued frequencies ω) indicating the stability characteristics of a given mode. Due to the non-linear dependence of the flame transfer function with ω, eigenvalues are found with a non-linear root-finding method. The acquired results met those obtained experimentally, indicating that the proposed model is capable of predicting the thermoacoustic behaviour of the combustion chamber.

Copyright © 2019 by ASME.Organized structures in turbulent jets can be modeled as wavepackets. These are characterized by spatial amplification and decay, both of which are related to stability mechanisms, and they are coherent over several jet diameters, thereby constituting a noncompact acoustic source that produces a distinctive directivity in the acoustic field. In this review, we use simplified model problems to discuss the salient features of turbulentjet wavepackets and their modeling frameworks. Two classes of model are considered. The first, that we refer to as kinematic, is based on Lighthill's acoustic analogy, and allows an evaluation of the radiation properties of sound-source functions postulated following observation of jets. The second, referred to as dynamic, is based on the linearized, inhomogeneous Ginzburg-Landau equation, which we use as a surrogate for the linearized, inhomogeneous Navier-Stokes system. Both models are elaborated in the framework of resolvent analysis, which allows the dynamics to be viewed in terms of an input-ouput system, the input being either sound-source or nonlinear forcing term, and the output, correspondingly, either farfield acoustic pressure fluctuations or nearfield flow fluctuations. Emphasis is placed on the extension of resolvent analysis to stochastic systems, which allows for the treatment of wavepacket jitter, a feature known to be relevant for subsonic jet noise. Despite the simplicity of the models, they are found to qualitatively reproduce many of the features of turbulent jets observed in experiment and simulation. Sample scripts are provided and allow calculation of most of the presented results.

© 2019 Cambridge University Press. All rights reserved.The current work presents a realizable method to control streaky disturbances in boundary layer flows and delay transition to turbulence by means of active flow control. Numerical simulations of the nonlinear transitional regime in a Blasius boundary layer are performed where streaks are excited in the boundary layer by means of a high level of free-stream turbulence. The occurring disturbances are measured by means of localized wall-shear-stress sensors and damped out using near-wall actuators, which resemble ring plasma actuators. Each actuator is powered by a time-varying signal whose amplitude is computed by processing signals from the sensors. The processed signal is the result of two control laws: The linear quadratic Gaussian regulator (LQG) and the inverse feed-forward control technique (IFFC). The use of the first control method, LQG, requires a state-space representation of the system dynamics, so the flow is described by means of a linear time-invariant operator that captures only the most relevant information of the dynamics and results in a reduced-order model (ROM). The ROM is computed by means of the eigensystem realization algorithm (ERA), which is based on the impulse responses of the real system. Collecting such impulse responses may be unfeasible when considering free-stream turbulence because of the high dimensionality of the input forcing needed for a precise description of such a phenomenon. Here, a new method to identify the relevant system dynamics and generate the needed impulse responses is proposed, based on additional shear-stress measurements in an upstream location. Transfer functions between such measurements and other downstream sensors are obtained and allow the derivation of the ERA system, in a data-driven approach that would be realizable in experiments. Finally, in order to discuss the advantages of the LQG based on the ROM and analyse its performance, the implemented LQG is compared to the IFFC, which consists of wave cancellation. The work (i) presents a systematic and straightforward way to deal with high-dimensional disturbances in order to build ROMs for a feasible control technique, and (ii) shows that even when considering practical constraints, such as the type and size of actuators and sensors, it is possible to achieve at least as large delay of bypass transition as that obtained in more idealized cases found in the literature.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.In this work we investigate the use of multiple-input, multiple-output (MIMO) transfer functions obtained empirically from a large-eddy simulation of a turbulent jet. We compare the MIMO performance with single-input-single-output (SISO) transfer functions used in previous studies. The choice of sensor placement has been made based on results of linear stability analysis from the literature. The results show that MIMO transfer functions improve on SISO results where both single-and two-point statistics are concerned. It is also found that the number of sensors necessary to converge the estimates depends strongly on Strouhal number.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Azimuthally coherent low-energy structures in the form of wavepackets are documented to play dominant role in sound radiation by subsonic turbulent jets. In earlier work, we have shown evidence of a coupling between the turbulent nozzle boundary-layer (NBL) disturbances and wavepackets in a M=0.9 turbulent jet, by means of two point statistics.1 The purpose of this study is to characterise the structures within the NBL using a high-fidelity large-eddy simulation of a M=0.4 turbulent jet. We first employ Spectral Proper Orthogonal Decomposition (SPOD) to the axisymmetric component of the flow in order to distill a low-rank approximation of the flow dynamics. This reveals the existence of coherent structures within the NBL and shows that these are correlated with wavepackets in the jet. We then model the NBL structures via a mean-flow stability analysis. Projection of the leading SPOD modes on the stability eigenmodes shows that the organised boundary layer structures can be modelled using a small number of stable eigenmodes. Finally local resolvent analysis of the mean-flow is performed. It is shown that the most-energetic nozzle structures can be succesfully modelled with optimal resolvent response modes.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Large scale, elongated structures, similar those ones widely studied in wall-bounded flows, are also present in turbulent jets. Several characteristics of these streaks can be identified via reduced order models such as resolvent analysis. The present work involves a resolvent-based study of these structures in turbulent jets. We focus on obtaining the optimal forcing that generates these energetic coherent structures. Results are compared with experimental data post-processed using spectral proper orthogonal decomposition, allowing us to draw conclusions about the nature of the non-linear forcing, since the two analyses should provide equivalent results if this term is modelled as spatially white. By identifying streaks in a global framework, we expect to better understand the mechanism by which they are generated.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.�Wavepacket models have been used extensively to predict the noise produced by turbulent subsonic and supersonic jets. Such wavepackets, which represent the organised structures of the flow, are solutions to the linearised Navier-Stokes equations. Using a kinematic two-point model, Wong et al. [1] have indicated the importance of incorporating coherence decay in modelling broadband shock-associated noise (BBSAN) in supersonic jets. In this work, we aim to improve the shock-noise model by using solutions from linear parabolised stability equations (PSE) to model the wavepacket part of the BBSAN source. The two-point coherence of the wavepackets is obtained from large-eddy simulation (LES) data of a Mj = 1.5 fully-expanded isothermal supersonic jet [2]. The aim is to build a dynamic sound-source model for BBSAN that would improve on the simplified line-source model proposed by Wong et al. [3]. We find that a frequency dependent coherence decay length scale is important in order to suppress the higher-order harmonic peaks [4] and to obtain the correct BBSAN peak shape. Moderate agreement up to St = 1 was found between the current noise predictions and those from experimental data.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The Parabolized Stability Equations (PSE) method has been extensively employed to compute the evolution of hydrodynamic instabilities in sheared flows. In its compressible-flow formulation, this method may also be used to compute sound propagation. Duct acoustics, in particular, may greatly benefit from its use, because complex boundary conditions and base-flows, including acoustic liners and developing boundary-layers, could be incorporated in the method. Furthermore, the PSE method is much less computationally demanding than standard numerical duct acoustics techniques. Aiming at unveiling this untapped potential, this work assessed the capabilities of PSE to predict sound propagation in cylindrical ducts. The acoustic field predicted with the PSE method for several simple duct models was compared with literature results. There was close agreement for ducts with uniform flow/constant wall impedance, sheared flow and axially varying base-flow temperature. The acoustic field predicted by the PSE for a duct with axially varying impedance displayed the expected trends and demonstrated that the method is able to account for such variation. Finally, prediction of acoustic propagation in a duct with turbulent boundary-layer showed that the PSE method can capture refraction and viscous dissipation of sound. These results showed that the method is able to accurately predict sound propagation through realistic duct models and is frugal with computational resources. We expect that the unveiled potentialities of the PSE method pave the way for faster acoustic liner design/optimization and deeper understanding on phenomena like liner instability.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.We present a numerical method to compute the acoustic scattering by an arbitrary geometry through resolvent analysis, allowing a classification of source distributions into optimal and suboptimal with respect to their acoustic radiation. A boundary element method (BEM) is applied to solve the Helmholtz equation for a discretisation of a source distribution, and the computed pressure for each source element is used to construct the resolvent operator, which is the product of a tailored Green’s function GT and quadrature weights. To understand how the acoustic field can be modelled, the optimal harmonic forcing and the associated linear response of the flow are obtained using a singular value decomposition of the linear resolvent operator. This was performed for two different cases. The first case is a semi-infinite flat plate, a case that has an analytical tailored Green’s function available in the literature, so a numerical approximation of the resolvent operator is directly obtained by multiplying the integration weights by a discretisation of GT. Results show the optimal forcing for sources close to the plate as a quadrupole distribution concentrated at the vicinity of the trailing edge. The associated responses have the expected cardioid directivity in the far field, with variations of this for higher-order resolvent modes. In the second case we analyse three different NACA airfoils, 0012, 4412 and 0018, where the tailored Green’s function was obtained numerically, and used to build the resolvent operator. Results for three different acoustic wavenumbers k0 show that the optimal forcing has dominant contributions from the leading and trailing edge regions, as well as a relevant region near the upper and lower surfaces, where typical boundary-layer fluctuations would act. The associated response for the largest k0 in the acoustic field is a scattering cardioid with secondary scattering due to the presence of a leading edge, as expected. Resolvent analysis can also be used to decompose model sources into forcing-mode components, which lead to far-field sound given by the response modes weighted by the gains; this is carried out here for a sample harmonic source. The present methods can be used as a novel analysis tool for aeroacoustic problems, isolating clearly dominant source mechanisms with high acoustic efficiency.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The effect of addition of viscoelastic layers on the acoustic scattering quadrupoles near the trailing edge of composite plates is evaluated. For modelling of the viscoelastic material the complex modulus approach was used in combination with the frequency-temperature correspondence principle. The computation of laminate stiffness is based on Classical Lamination Theory. We employ a numerical method to compute the acoustic field scattered by finite elastic plates. Based on a Boundary Element Method, this procedure solves the Helmholtz equation subject to boundary conditions related to the vibration of the plate. These conditions are recast in terms of the vibration modes of a rectangular plate. Results show that by adding viscoelastic plies to a composite plate we modify the far-field sound scattered by turbulence near an edge of the plate. Parametric studies show that this approach reduces scattered noise at resonance frequencies. Discussions on the operating temperature, positioning and thickness of the viscoelastic layers are provided.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Hydrodynamic instabilities are directly related to large-scale coherent structures that are correlated with jet noise emission. Unravelling and accurately predicting their fundamental dynamics shows a promising direction for designing quieter jet engines. In this study, we analyze high-fidelity large-eddy simulation data of a turbulent Mach 0.4 round jet and a Mach 1.5 chevron jet. Using spectral proper orthogonal decomposition we identify, beyond the well-known1 Kelvin–Helmoholtz and Orr mechanisms, elongated alternating streamwise streaks of high and low-speed fluid that have been associated with a non-modal lift-up effect in wall-bounded shear flows. In the global three-dimensional domain, the most energetic streaks manifest for azimuthal wavenumber m = 1 and frequency St → 0. Furthermore, for the chevron jet, streaks and streamwise vortices appear due to the presence of the serrated nozzle, and they inherit the periodicity of the nozzle geometry. Finally, local (planar) spectral proper orthogonal decomposition is used to analyze the coherent structures of the chevron jet flow. Near the nozzle exit, antisymmetric and symmetric modes appear to be amplified and linked to the presence of the chevrons/streaks. Further downstream, the most energetic modes share similar characteristics to the ones observed in round jets.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The present work is dedicated to the modelling of the low-frequency part of the jet-plate interaction noise in flight conditions. An analytical model used in the work is based on the scattering of jet near-filed hydrodynamic pulsations, represented in terms of azimuthal modes, by the plate trailing edge. Unlike the static case, in the presence of a co-flow it is difficult to measure directly the azimuthal structure of the pressure in the jet near-field. In the present work, we use the technique based on the hot-wire measurements on the jet axis. This approach allows measuring velocity fluctuations related to the axisymmetric mode. The agreement found between a parabolized stability equations (PSE) model and experimentally measured velocity fluctuations on the jet axis allows using the PSE approach for reconstruction of the pressure field of the axisymmetric mode in the vicinity of the plate trailing edge in static and flight conditions. These pressure characteristics are then used as input in the analytic jet-plate interaction noise model. It is shown that this analytic model informed by PSE-reconstructed pressure field is capable to capture the main features of low-frequency jet-plate interaction noise in the presence of co-flow.

© 2019 Cambridge University Press. All rights reserved.This work deals with the closed-loop control of streaky structures induced by free-stream turbulence (FST), at the levels of 3.0Â % and 3.5Â %, in a zero-pressure-gradient transitional boundary layer, by means of localized sensors and actuators. A linear quadratic Gaussian regulator is considered along with a system identification technique to build reduced-order models for control. Three actuators are developed with different spatial supports, corresponding to a baseline shape with only vertical forcing, and to two other shapes obtained by different optimization procedures. A computationally efficient method is derived to obtain an actuator that aims to induce the exact structures that are inside the boundary layer, given in terms of their first spectral proper orthogonal decomposition (SPOD) mode, and an actuator that maximizes the energy of induced downstream structures. All three actuators lead to significant delays in the transition to turbulence and were shown to be robust to mild variations in the FST levels. Integrated total drag reductions observed were up to 21Â % and 19Â % for turbulence intensity levels of 3.0Â % and 3.5Â %, respectively, depending on the considered actuator. Differences are understood in terms of the SPOD of actuation and FST-induced fields along with the causality of the control scheme when a cancellation of disturbances is considered along the wall-normal direction. The actuator optimized to generate the leading downstream SPOD mode, representing the streaks in the open-loop flow, leads to the highest transition delay, which can be understood due to its capability of closely cancelling structures in the boundary layer.

© 2019 International Symposium on Turbulence and Shear Flow Phenomena, TSFP. All rights reserved.Fully resolved direct numerical simulations, performed with a high-order spectral-element method, are used to study coherent structures in turbulent pipe flow at friction Reynolds numbers Reτ = 180 and 550 (El Khoury et al., 2013). The database was analysed using spectral proper orthogonal decomposition (SPOD) so as to identify dominant coherent structures, most of which are of streaky shape. As a reduced-order model for such structures, the linearised flow response to harmonic forcing was computed, and the analysed singular modes of the resolvent operator were analysed. For turbulent flows, this approach amounts to considering the non-linear terms in the Navier–Stokes system as an unknown forcing, treated convenienty as external. Resolvent analysis then allows an identification of the optimal forcing and most amplified flow response; the latter may be related to observed relevant structures obtained by SPOD, especially if the gain between forcing and response is much larger than what is found for suboptimal forcings or if the non-linear forcing is white noise. Results from SPOD and resolvent analysis were extracted for several combinations of frequencies, streamwise and azimuthal wavenumbers. For both Reynolds numbers, good agreement between SPOD and resolvent modes was observed for parameter combinations where the lift-up mechanism is present: optimal forcing from resolvent analysis represents streamwise vortices and the associated response are streaky structures.

© Proceedings of the 26th International Congress on Sound and Vibration, ICSV 2019. All rights reserved.This work has as main objective to analyse experimentally the influence of the effects of the flexibility in the sound emissions of trailing-edge extensions in aeronautical structures. For this, an experimental apparatus installed in a cavitation tunnel was used, whose working fluid is water. Flow was studied around a rigid NACA 0012 profile with interchangeable flexible trailing edge extensions. Two flat metal plates with different thicknesses were used as extensions, leading therefore to different values of flexural stiffness. The purpose of such tests is to obtain high Reynolds numbers, low Mach numbers and high fluid-structure loading factors (related to the ratio of fluid and solid densities). Which enhances fluid-structural interactions; acoustic effects are captured with a hydrophone installed in acoustic chamber in the section of tests. This analysis allows to make comparisons of the experimental results with predictions from aeroacoustic theory. Increasing the flexibility of the trailing edge, according to this theory, reduces aeroacoustic and hydroacoustic emissions. However, the experimental results obtained show the opposite effect: the more flexible trailing edge led to a greater sound radiation. The results suggest that there is significant changes in turbulence due to the effect of the trailing edge vibrations; a possible increase in turbulent kinetic energy due to surface vibration could explain the present results

© 2019 The Author(s) Published by the Royal Society. All rights reserved.We investigate the effects of structural damping on the interaction of a turbulent eddy with flexible plates with respect to the efficiency of aerodynamic noise generation. Potential benefits are studied using a model based on a point-reacting compliant semiinfinite plate on a spring-damper foundation. This scattering problem is solved using the Wiener- Hopf technique. We compare results for semi-infinite compliant plates with finite ones. In both cases, plate vibration lead to reductions of sound radiation, especially at resonance; damping tends to reduce such acoustic benefits. We also present a formulation that considers the effect of structural damping on the acoustic properties of finite elastic plates. Numerical results are obtained by applying a boundary element method to solve the Helmholtz equation subject to the boundary conditions imposed by the plate vibration. Under specific conditions, such as high fluid loading factor and low bending-wave Mach number, the acoustic power scattered by an edge tends to be smaller than that which propagates over the plate as bending waves. Results show that structural damping attenuates these waves and may modify the far-field acoustic pressure, mostly by reducing the scattered sound at structural resonances. All models show that large damping coefficients lead to locally overdamped responses. There is thus an ideal range of structural damping to reduce both plate vibration and acoustic scattering.

© 2019 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The dominant acoustic radiation from turbulent jets has been associated with coherent wave-packet structures in the plume. Jet noise models are therefore often designed using the statistics of decomposed coherent fluctuations, which display wave-packet attributes. In the absence of a universal definition for wave-packet fluctuation components, several approaches have evolved to educe wave packets. These include pressure and velocity variables that are typically processed through azimuthal and/or proper orthogonal decompositions to yield different models. Large-eddy simulation database of a Mach 0.9 jet is used to suggest a unifying candidate field to obtain wave-packet statistics. The statistical properties of this acoustic mode, which comprises the irrotational-isentropic constituent of momentum fluctuations, are tested to show that it properly reproduces wave-packet statistics known to be crucial for acoustic modeling. Compared to raw pressure fluctuations, the acoustic wave packet essentially filters out the high-energy hydrodynamic fluctuations, optimally reconstructs the near- and far-field acoustic radiation, and recovers wave-packet properties with superior spatiotemporal coherence and radiative efficiency. The inherent difference between the acoustic wave packet and the pressure field is related to the distribution of phase speeds of the respective signals. These features of the acoustic mode are then used to generate a two-point wave-packet model for downstream radiation from this jet.

© 2019 Elsevier Masson SASAmong the aeroelastic phenomena most commonly affecting flexible and very flexible aircraft, those caused by gusts deserve special attention due to their potential either in degrading flying qualities and ride comfort or in increasing structural loads. It is then of interest to structural loads and flight controls engineers that solutions be developed to attenuate the effects of gusts on aircraft. Particularly, the use of piezoelectric transducers arises as one of the potential solutions in the design of gust load alleviation and structural mode suppression systems. In this paper, the gust load alleviation on a flexible smart idealized wing using only piezoelectric transducers is analyzed and experimentally tested. The numerical model includes a finite-element model of the wing, employing two-node, seven-degree-of-freedom smart beam elements, assuming small deformations and neglecting transverse shear. A quasi-steady, strip-theory-based aerodynamic model is used. Two control laws are evaluated: one based on output feedback, and the other based on feedback of observed states of a truncated system. Using a gust generator, wind-tunnel tests were performed at different flow speeds and gust frequencies to validate the computational model and to verify the performance of piezoelectric transducers. The results show a considerable attenuation of the wing root bending moment, especially using two piezoelectric actuators. Important performance improvements were overall verified with feedback of observed states when compared with static output feedback, specially to decrease the participation of the elastic modes in the gust response.

© Universal Technology Corporation, 2018.The advent of modern fly-by-wire systems permitted the development of dedicated control law functionalities focused on enhancing aircraft’s performance, increasing safety and reducing pilot workload. However, these control laws use digital sensors to measure aircraft parameters that can be affected by the elastic-body dynamics, such as angle-of-attack, sideslip angle, Euler angles and angular rates. The introduction of notch filtering is a strategy typically used to decouple rigid and elastic-body dynamics, allowing the implementation of control laws that will not harm aircraft’s structural integrity. In this paper, we compare a traditional stability-augmentation system based on notch filtering and feedback of rigid-body states with a more sophisticated system that allows feedback of the aeroelastic modes. For a fair comparison, the same constraints regarding aeroelastic modes attenuation are considered for both control system strategies. The comparison is made by investigating the effects of both stability-augmentation systems control strategies on the handling qualities upon the analysis of frequency domain criteria and by pilot-in-the-loop simulations considering high-gain maneuvers, such as the pitch capture maneuver. Effects of variation of airframe elasticity level are also considered under this scope.

© Universal Technology Corporation, 2018.There are many challenges related to the design and operation of flexible aircraft. Flight control law design for improving handling qualities is one of them because the major problem in the design of controllers then concerns aeroservoelastic stability. To deal with this difficulty, methodologies for flight control law design considering the aeroelastic dynamics of the aircraft are being pursued. In this paper, an output-feedback-based stability augmentation system is proposed and designed to improve the handling qualities of a flexible aircraft and to increase the structural damping of some of its aeroelastic modes. The design is based on the projective control technique, which allows preserving in the closed-loop system the eigenstructure of certain modes of interest whose dynamic characteristics stem from an optimal state feedback solution. The X-HALE flexible aircraft is considered. Numerical studies by means of nonlinear simulations allow testing and confirming the effectiveness of the proposed controller.

© Universal Technology Corporation, 2018.The development of modern, more efficient transport aircraft and High-Altitude-Long-Endurance (HALE) aircraft requires solutions that involve lightweight structures and high aspect ratio wings for maximum aerodynamic efficiency. However, this may result in flexible wings, such that the coupling between rigid-body and structural modes deteriorates stability and handling qualities of the aircraft. These can be improved by the continuous operation of control systems with the use of structural information, such as wing deformed shape. Strain gages can be used for such an application. However these sensors may have input interference, such as temperature variation, that can cause false strain responses other than the expected measurements due to flight loads. This work presents the analyzes of strain gage measurements due to thermal loads in the X-HALE aircraft wing. Three thermal correction methods were proposed: functions of temperature, dummy gage, and high-pass filtering. Each was tested on indoor and outdoor experiment setup, which uses a lamp and natural temperature variation throughout a full day as heat sources. All methods were effective in removing thermal drift of indoor experiment data. However, only high-pass filtering method was successful in the outdoor experiment. Indoor thermal test results done on the full 4m X-HALE aircraft, with the addition of impact excitations on the aircraft’s wing tip, showed that the high-pass filtering was able to remove thermal drift while maintaining all responses in the frequency range of interest. Therefore, this method is suitable to the present application.

© Universal Technology Corporation, 2018.Biodynamic feedthrough is a phenomenon in which structural vibrations on the cockpit are fedback to the pilot, who transmits those vibrations on the aircraft through involuntary inceptor displacements. In the case these commands lead to instabilities, the phenomenon is then called Pilot-Assisted (or Augmented) Oscillations (PAO). This is a complex phenomenon that depends on three basic elements. First element is the aeroelastic modes of the aircraft, especially their modal shapes (since only specific modal shapes interfere in this phenomenon) and frequencies. Second one is the inceptor’s system characteristics, such as natural frequency and damping. The last element is the human pilot dynamics, which may be modelled as a passive spring-mass-damper system. This paper aims to explore how these three elements affect the development of the PAO phenomenon for more flexible aircraft. The investigations herein are accomplished for a virtual, flexible aircraft by the analysis of pilot-in-the-loop simulations of a high gain maneuver, varying airframe elasticity levels, inceptor system parameters and pilot model characteristics.

© Universal Technology Corporation, 2018.Formulations for the flight dynamics of flexible aircraft have been commonly applied to aircraft having all six rigid-body degrees of freedom unconstrained. However, during takeoff and landing, the aircraft motion becomes constrained by the ground. An intricate dynamical problem arises when the flexible aircraft has multiple underwing pod-mounted landing gears. During liftoff, the most outboard landing gears become airborne earlier than the most inboard ones. The equations of motion used in a simulation model must then include time-varying ground constraint forces. Aerodynamically, the ground effect becomes relevant and can be modeled using the method of images. Wheel-to-ground rolling resistance also needs to be considered. This paper aims at the derivation of equations of motion that allow simulating the takeoff of such complex aircraft configurations. The developed formulation is important because it is readily applicable also to the landing phase, allowing the calculation of landing loads and the design of takeoff and landing control systems with less uncertainties. As spinoffs, the stability analysis of flexible aircraft in ground effect and evaluation of takeoff performance are also made possible.

© Universal Technology Corporation, 2018.An analysis of the flight dynamics of flexible aircraft having high-aspect-ratio wings shows that, even if the elastic deformations are not large enough to incur structural-dynamic geometrical nonlinearities, important aerodynamic effects can arise that are geometrically nonlinear in essence. For instance, the dihedral effect of the deformed wing is usually significantly different from that of the undeformed one, leading to unacceptable inaccuracies when analyzing the aircraft response to side gusts. Classical approaches to the aeroelastic modeling of flexible aircraft, using geometrically-linear finite elements, the vortex- or doublet-lattice methods, and linear or surface spline interpolation techniques, are unable to represent aerodynamic geometrical nonlinearities, because all the aeroelastic model matrices are calculated a priori for the undeformed aircraft and remain unchanged in the analysis. However, numerical experimentation indicates that, if small deformations occur, then the aerodynamic geometrical nonlinearities can be approximately modeled with an on-line update of the spline matrices to take into account the instantaneous deformed normal directions, without the need to perform the much costlier aerodynamic mesh deformation. This paper aims at the derivation of the equations for the modified generalized aerodynamic forces and at the validation of the proposed method in both static and dynamic conditions.

© Universal Technology Corporation, 2018.Previous works evidenced stability problems associated with flight control law design for flexible aircraft. In this paper, a fuzzy-based gain-scheduling approach is proposed to adequate closed-loop response. An interactive method that aims performance improvement while enforcing global stability considering fuzzy gain-scheduling was proposed. The application of the technique was demonstrated for the flexible X-HALE aircraft nonlinear model and compared to classical interpolation-based gain-scheduling techniques. Results revealed that fuzzy-based gain-scheduling is promising for flexible aircraft control.

© 2019 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.Control law design for flexible aircraft with coupled structural and rigid-body dynamics is currently a challenge. This paper aims to improve the dynamical characteristics of a flexible aircraft by proposing a performance index for stability augmentation system design. The theoretical formulation will be presented, comparisons of numerical results between open-loop and closed-loop systems will be made and, finally, experimental data obtained via flight tests will be shown.

© 2019 by Daniel Drewiacki, Flávio José Silvestre, and Antônio Bernardo Guimarães Neto.The advent of fly-by-wire technology brought many advantages to aircraft design, but also increased the number of occurrences of the undesirable pilot-induced oscillation phenomena. To analyze such phenomena, handling qualities criteria have been established, mostly in the frequency domain. In the time domain, dynamic models to represent pilot behavior have been proposed for pilot-in-the-loop analysis and simulations. Both cases assume the aircraft as a rigid body. For more flexible aircraft, this approximation is no longer valid, and aeroelastic dynamics may interact with both flight dynamics and pilot body dynamics, possibly leading to the occurrence of other issues, such as biodynamic feedthrough. In this paper, the importance of considering the influence of airframe flexibility in the study of the pilot-induced oscillation phenomena is addressed by the application of handling qualities criteria using a flexible aircraft dynamic model.

� 2019, Associacao Brasileira de Divulgacao Cientifica. All rights reserved.Diamond-like carbon (DLC) film is a biocompatible hard coating material that can prevent the leaching of metal ions. This study evaluates the structural characteristics of DLC, with and without silver nanoparticles, deposited by plasma (PECVD) on titanium alloy (Ti-6Al-4V) and bone formation in contact with DLC films. Sixty Ti-6Al-4V samples were used divided in: Uncoated, coated with DLC and coated with DLC-Ag. After structural characterization, samples were fixed bilaterally at the rabbit's mandible. After 15 and 90 days, samples were characterized again and bone formation in the area was analyzed by histomorphometry. Statistical analysis was performed by two-way ANOVA. Both the DLC and DLC-Ag films were firmly adhered and showed a high electrical resistance without significant changes in the Raman spectrum after in vivo integration. After 15 days, there were immature bone trabeculae in the interface and partially covering the surface. After 90 days, mature bone filled the interface and coved the surface. There was no statistically significant difference among the three groups in both periods. In conclusion, osseointegration with DLC, DLC-Ag and uncoated Ti-6Al-4V is similar. However, DLC and DLC-Ag coverings have the advantage of electrical insulation and can presumably control bacterial activity and ion leaching.

© 2019 John Wiley & Sons Australia, Ltd.AIM: To analyze the effect of a silicon (Si)-based film deposited on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) on the topography and bond strength of resin cement. METHODS: Specimens of zirconia were obtained and randomly divided into 4 groups, according to surface treatment: polished group (PG) zirconia; sandblasted group (SG) zirconia with aluminum oxide (100 µm); after polished, zirconia was coated with Si-based film group (SiFG); and after sandblasted, zirconia was coated with Si-based film group (SiFSG). The Si-based films were obtained through plasma-enhanced chemical vapor deposition. Surface roughness and contact angle analysis were performed. Resin cement cylinders were built up on the treated surface of blocks, after applying Monobond-S. The specimens were submitted to thermocycling aging and shear bond strength testing. The Kruskal-Wallis and Mann-Whitney U-tests were performed. RESULTS: There were significant differences between the surface treatments for each roughness parameter measured. Si-based film increased roughness and decreased the contact angle. Si-based film groups also demonstrated significantly lower bond strength values. CONCLUSION: Si-based film produced using plasma deposition provided lower bond strength to resin cement compared with conventional treatment; however, the film deposition reduced the contact angle and improved roughness, favorable properties in the long way to prepare an optimum material.

© 2019Increasingly more young patients have been submitted to reconstruction of the Temporomandibular Joint (TMJ), so, the prostheses must to present more functional longevity. Objective: To evaluate the effect of diamond-like carbon film (DLC)over titanium alloy (Ti6Al4V)and polyethylene (UHWPE)samples, their mechanical and chemical properties and cellular cytotoxicity. Methods: Titanium and UHWPE specimens, with 2.5 cm in diameter and 2 mm thickness were coated through plasma enhanced chemical vapor deposition (PECVD)with DLC or DLC doped with silver (DLC-Ag). Scanning electron microscopy (SEM)morphological analysis, Energy-dispersive spectroscopy (EDS)chemical analysis, scratching test, mechanical fatigue test, surface roughness analysis, and cellular cytotoxicity were performed. Data were statistically analyzed using one-way ANOVA (p < 0.05)or two-way ANOVA and multiple comparison Tukey test. Results: In the SEM analysis, morphological differences were observed on substrates after DLC deposition. The film chemically modified the substrate surfaces, according to the EDS analysis. The initial critical load failure occurred at 6.1 N for DLC and 9.7 N for the DLC-Ag film. The DLC film deposition over the polyethylene promoted a decrease in the polymer's damaged area after mechanical fatigue cycling. The cytotoxicity analysis demonstrated less biocompatibility in experimental groups, when compared to control, however, increased biocompatibility was observed, at 10 days, in all groups. Conclusion: The diamond-like carbon coating enhanced the chemical and mechanical properties from substrates, however modified biological interaction course of the titanium alloy (Ti6Al4V)and polyethylene (UHWPE)samples. Parameters for film deposition remain to be improved in order to obtain best biocompatibility.

© 2019 by the authors. The Ti-6Al-4V alloy is widely used in the manufacture of components that must have low density and high corrosion resistance and fatigue strength. The fatigue strength can be improved by surface modification. The aim of this study was to determine the influence of plasma nitriding on the fatigue behavior of a Ti-6Al-4V alloy with a lamellar microstructure (Widmanstätten type). Nitriding was executed at 720 °C for 4 h in an atmosphere with N 2 , Ar, and H 2 . Microstructure characterization of the samples was carried out by X-ray diffraction analysis, optical microscopy, and scanning electron microscopy. The average roughness of the specimens was determined, and fatigue tests were executed in a bending-rotating machine with reverse tension cycles (R = -1). X-ray diffraction analysis of the nitrided alloy revealed the following matrix phases: α,β, ε-Ti 2 N, and δ-TiN. A nitrogen diffusion layer was formed between the substrate and the titanium nitrides. Plasma nitriding resulted in an increase in low-cycle fatigue strength, whereas at high cycles of 200 MPa, both conditions exhibited similar behaviors. The fracture surface of the fatigue-tested specimens clearly revealed the lamellar microstructure. The fracture mechanism in the non-nitrided specimens appears to be due to cracking at the interface of the α and β phases of the lamellar microstructure.

© 2019 Trans Tech Publications Ltd, Switzerland.Ti alloys have been intensely used for human implants due to its excellent characteristics, like bio-inertness, low density, and corrosion resistance. However, some alloying elements were found to be toxic for the human body, which restricts the use of some alloys. Furthermore, there are two additional and essential aspects to be considered. The first relates to the young modulus that, despite being lower than other alloys commonly used for this purpose, it is still far over from the human bone modulus. Such high modulus can result in the stress shield phenomena and the consequent implant losing. The second aspect relates to the fact that bio-inertness does not guarantee a complete tissue integration to the implant and, consequently, the expected implant performance. In this context, new low modulus β-Ti alloys containing nontoxic elements have been developed in recent years, and several surface modification processes have been proposed to promote better implant/tissue integration. In the present work, the new β-type Ti-Mo-Zr-Fe alloy has been submitted to a plasma enhanced chemical vapor deposition (PECVD) process in order to form a superficial titanium nitride layer, aiming to produce a satisfactory substrate for the tissue cells growing. In a first step, microstructural characterization and corrosion performance of the modified alloy surface has been evaluated by Electrochemical Impedance Spectrometry and Potentiodynamic testing, and the results compared to the unmodified alloy. It was found that during the plasma nitriding process, that runs at 550oC for 1h, the metastable β microstructure is partially converted into α’ and possibly α” phases, which can impact the young modulus. The 500nm thick TiN layer formed over the alloy surface improved the corrosion behavior of the alloy. These results encourage the continuity of the research, with the future in vitro bio-activity testing of the nitrided surface.

© The Authors, published by EDP Sciences, 2019.Current energy conversion machines such as the micro gas turbine can be improved by harvesting the low-grade energy of the exhaust. A prominent option for such is the organic Rankine cycle due to its relatively efficient and reliable design. This manuscript presents a review on the subject and is the first step toward the design of an organic Rankine cycle bottoming a 100 kWe recuperated gas turbine. After introducing and covering the historical development of the technology, appropriate guidelines for defining the cycle arrangement and selecting the fluid are presented. At last, the viability of the cycle is assessed by assuming an appropriate efficiency value and general cost functions. The organic Rankine is expected to generate an additional 16.6 kWe of power, increasing the electrical efficiency from 30 to 35%. However, the capital cost increase was estimated in 48%.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work presents and analyzes the suitability of using differential GPS equipment (DGPS) for the determination of air data system errors by means of flight testing of the H-50 (AS 350) helicopter. Since the Pitot-error cannot be undervalued, two existing methodologies that use the DGPS as a data acquisition tool have been adapted for the usage in helicopters. Results of flight tests using a validated technique (tower flyby and ground speed course) are presented for the purpose of comparison with data obtained from both proposed techniques. Data are processed through mathematical equations and specific code in MatLab® platform, which has been adapted specifically for this research. Two methodologies using DGPS are set: the first needs three stabilized legs for each speed within the desired flight envelope whose trajectory describes a path similar to a clover leaf, which suggests the method's name: "cloverleaf"; The second uses acceleration and deceleration in 90 degrees alternated legs forming a windbox-like design. The data reduction is performed by iterations of the estimated parameters until a convergence criterion is reached using the analysis of the outputs. Results show the suitability of both proposed methods from a quantitative point of view. Qualitatively, the windbox maneuver with parameters estimation from the analysis of output-error allows reducing material resources expenditures without quality degradation.

© 2019, Avestia Publishing.In an effort to ensure the robustness and numerical stability of a three-dimensional explicit compressible code for all speed flows, a preconditioning technique was implemented. The code solves Euler steady-state equations into a three-dimensional flow. Local preconditioning was implemented due to their accuracy in predicting lift and drag forces on mixed flows. However, for low speed flows near stagnation points numerical perturbations are amplified, generating a loss in the convergence rate, code accuracy and robustness. Aiming to improve the preconditioning accuracy and convergence rate suggested a new limit to the preconditioning sensor based on the flow pressure. Numerical simulations of a subsonic flow over a cylinder showed a faster convergence rate when the preconditioning technique was implemented.

© 2019, Avestia Publishing.In this paper are presented a preconditioning technique to be implemented in a three-dimensional explicit compressible code to solve a turbulence flow to steady state regime. A local preconditioning technique with accurate predictions of mixed speed regimes is implemented in the original code, however, for low flow Mach numbers in the boundary layer region the numerical accuracy is lost to the preconditioning code. To improve the numerical solution are suggested a new limit to the preconditioning sensor based on a pressure sensor and is established an explicit flux function to evaluate the preconditioning sensor in the cell fluxes. The preconditioning code is validated for a supersonic case in nozzle and then to a subsonic case is studied the convergence rate for a low Mach number flow. Numerical solutions demonstrated that the changes applied in the original code improves the accuracy and robustness of the code for low speed flows.

© 2019, Avestia Publishing.A computational program used to calculate the preliminary design of axial turbines which uses the Kacker and Okapuu's loss model was modified to improve the losses predictions implementing Tournier and El-Genk's loss model. The in-house program was written in FORTRAN 90 and is based on the meanline technique to calculate the axial turbine. As the losses interfere in the geometrical calculations applying more accurate loss models, the predictions of the preliminary design are more reliable. The program was applied to design a single-stage turbine and the results are compared with the commercial turbomachine design software AXIALTM®. The improvements obtained by applying a more recent loss model have been discussed as the future works to improve the in-house program.

© 2019 Inderscience Enterprises Ltd.This manuscript provides an exergy-based parallel between combined- A nd steam-cycle power plant configurations burning blast furnace gas (BFG). The combined cycle (CC) was based on a currently operational power plant located in Rio de Janeiro, Brazil. The steam cycle (SC) was created by replacing the gas turbines (GTs) for steam generators (SGs) that handled the same amount of fuel. The results show that the combined cycle achieved 21.25% higher exergy efficiency, although emitting twice as much nitrogen oxide. The combined cycle generated 52.08% less steam while wasting 78.86% less exergy, which indicated that steam generators benefit from a higher amount of excess air. The gas turbine combustion chamber high exergy efficiency indicates that burning low-grade fuels is beneficial for reducing the intrinsic waste of chemical reactions. However, the compression process required prior to combustion undermines this benefit. Ultimately, this manuscript provides a comparison between two options to avail blast furnace gas.

© 2019 ISAThe present paper is concerned with the dynamic modeling and design of control laws for a small non-rigid multi-rotor airship constituted of an oblate-spheroid helium balloon coupled with an electric-powered hexa-rotor airframe. The vehicle is assumed to operate in windless and low-speed conditions. A six-degree-of-freedom nonlinear dynamic model is derived for it using the Newton–Euler approach and considering, among other efforts, a restoring torque due to the displacement of the balloon's center of buoyancy above the vehicle's center of mass and the added-mass effect resulting from the air–structure interaction. Using the derived model and assuming a time-scale separation between the translational and rotational dynamics, the attitude and position control laws are designed separately from each other. Both laws are formulated using feedback linearization combined with control input saturation within appropriate parallelepipedal sets, which are carefully chosen to respect pre-defined bounds on the control torque, control force and maximum inclination angle. The effect of temperature and pressure fluctuations is taken into account through a parametric probabilistic approach, where Maximum Entropy Principle is used to construct a physically consistent stochastic model and Monte Carlo method is used as the stochastic solver to propagate the uncertainties through the system. Extensive simulation results show the effectiveness of the proposed control system and quantify the uncertainty of its performance over a wide range of local temperature and pressure.

© 2019 Elsevier Masson SASAmong the aeroelastic phenomena most commonly affecting flexible and very flexible aircraft, those caused by gusts deserve special attention due to their potential either in degrading flying qualities and ride comfort or in increasing structural loads. It is then of interest to structural loads and flight controls engineers that solutions be developed to attenuate the effects of gusts on aircraft. Particularly, the use of piezoelectric transducers arises as one of the potential solutions in the design of gust load alleviation and structural mode suppression systems. In this paper, the gust load alleviation on a flexible smart idealized wing using only piezoelectric transducers is analyzed and experimentally tested. The numerical model includes a finite-element model of the wing, employing two-node, seven-degree-of-freedom smart beam elements, assuming small deformations and neglecting transverse shear. A quasi-steady, strip-theory-based aerodynamic model is used. Two control laws are evaluated: one based on output feedback, and the other based on feedback of observed states of a truncated system. Using a gust generator, wind-tunnel tests were performed at different flow speeds and gust frequencies to validate the computational model and to verify the performance of piezoelectric transducers. The results show a considerable attenuation of the wing root bending moment, especially using two piezoelectric actuators. Important performance improvements were overall verified with feedback of observed states when compared with static output feedback, specially to decrease the participation of the elastic modes in the gust response.

© 2018 Elsevier LtdIn this work, viscoelastic materials are adopted for handling aeroelastic features of typical section models with three degrees-of-freedom, which present non-smooth, free-play type nonlinearities in their control surface. A rotational viscoelastic damper is added to the resilient element associated to the control surface motion of the typical section. Equations of motion are derived accounting for the viscoelastic damper dependence on frequency and temperature. For this, a fractional derivatives-based viscoelasticity constitutive law is considered. Aerodynamic forces are introduced based on linear potential unsteady aerodynamics accounting for arbitrary airfoil motions. The aeroelastic behavior is investigated through time domain simulations, from which bifurcation diagrams are constructed. Numerical results show that the addition of viscoelastic damping can increase the flutter speed noticeably and reduce the amplitudes of limit cycle oscillations for the system under consideration. Another observed benefit provided by the viscoelastic damper is that undesirable subcritical behavior for the bifurcation onset can be eliminated or modified to have a supercritical character. The influence of temperature on the aeroviscoelastic behavior is also investigated. Using the proposed strategy, nonlinear instabilities can be controlled, improving the safety margins of aeroelastic systems.

© 2019 ASMEIt has been amply demonstrated that the development of SMA actuators has a great potential of application in several branches of industry. Obviously, the efficiency of the actuators depends both on the inherent features of the materials they are made of and the geometric characteristics of the devices. This work considers a particular type of actuator first conceived by [1], consisting in the association of two cantilever beams, the first presenting the shape memory effect and the second presenting the superelastic effect, coupled mechanically so as to guarantee two equilibrium positions and thus a stand-alone cyclic actuator, in which the superelastic beam provides the bias action. Numerical simulations of the behavior of the actuator are performed using the commercial finite element software COMSOL, which implements the Boyd-Lagoudas thermomechanical model. The goal of the simulations is to characterize the actuation range of the actuator, in terms of maximum displacement obtained at the tip. The effect of the dimensions of the beams on the tip displacement under some load scenarios is investigated. The results provide guidelines for the design of the actuator to fulfill specific requirements, also suggesting the use of numerical optimization for the optimal design of the actuator accounting for constraints.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The uncertainty propagation of a stochastic random spatial field in the fiber volume applied to steered carbon reinforced composite plates designed for aeroelastic purposes is assessed. Based on the Karhunen-Loève expansion (KLE), considering fixed covariance functions, the lamina material properties are estimated using the mixture rule affected by the fiber volume spacing variation. The structural model is based on the Classical Lamination Theory considering symmetric stacking sequence and fiber trajectories described by Lagrange polynomials. Two distinct aeroelastic models are evaluated: i) modeled according to the quasi-steady aerodynamic model with the inclusion of the term of unsteadiness in pitch velocity; (ii) based on the piston theory for high Mach number approximation. The uncertainty propagation is done using the generalized polynomial Chaos (gpC) expansion to evaluate the flutter onset, flutter frequency and plate mass variabilities with computational efficiency.

Copyright © 2019 ASMEIn order to enhance competitiveness of rigid risers for the Brazilian pre-salt, great effort has been devoted to study the feasibility of Steel Catenary Risers (SCR) directly connected to Floating Production Storage and Offloading (FPSO) units, where cost savings are expected from the reduction of pipe buoyance modules and overall piping length. A recent paper presented the technical feasibility of Damped SCR, which is a new SCR concept. In that study, some non-field-proven fatigue performance improvements were required, such as girth welds for mechanically lined pipe (MLP) with increased fatigue strength and/or upset end pipes. During the development of this technology, a fracture mechanics approach became essential for the assessment of fatigue and fracture limit state in order to guarantee that the risks associated with fabrication and inspection are within acceptable safety levels. This paper presents the main issues related to fabrication and inspection activities with a particular focus on the smallest critical flaw size. A semi-deterministic Engineering Critical Assessment (ECA) was performed as part of the conceptual design. The uncertainties about input data are discussed and a simplified procedure is proposed. Results are compared with relevant nondestructive testing reliability statistics. This study indicates that the benefits obtained from the use of materials with superior fatigue resistance are limited to the non-destructive testing reliability at some degree. As the proposed methodology deals with uncertainty in input data, a roadmap for the development of a full probabilistic risk assessment of fabrication and inspection feasibility at early design stages is devised.

© 2019, Springer Nature Switzerland AG.This chapter is devoted to the use of viscoelastic materials as a strategy intended for passive vibration control in mechanical systems. It provides a review of the theoretical foundations underlying the constitutive modeling of the viscoelastic behavior, and the association of constitutive models with modern numerical resolution procedures, especially the finite element method. This currently enables the accurate prediction of the dynamic behavior of rather complex structural systems featuring viscoelastic dampers, duly accounting for the particular characteristics of the viscoelastic behavior, namely the memory effect and the dependence of stiffness and damping properties on frequency and temperature. Other relevant aspects considered are: (i) model condensation techniques, intended to reduce the computation cost involved in the evaluation of the response of viscoelastic structures using finite element models with large numbers of degrees-of-freedom; (ii) the identification of viscoelastic constitutive models from experimental data. In addition, some applications of viscoelastic materials to structures of engineering interest are presented to illustrate the use of some techniques discussed.

© 2018 by the American Institute of Aeronautics and Astronautics, Inc.The supersonic aeroelastic stability of tow-steered carbon reinforced composite panels, in each layer of which the fibers follow curvilinear paths, is assessed.Astructural model based on the Rayleigh-Ritz method, combined with the aerodynamic piston theory, is derived to represent the aeroelastic behavior of rectangular plates under different boundary conditions. In this model, the classical lamination theory, considering a symmetric stacking sequence and fiber trajectories described by Lagrange polynomials of different orders, is used. In addition, manufacturing constraints, which impose limitations to the feasible fiber trajectories, and the effect of in-plane loads are considered in the model. Using a multicriteria differential evolution algorithm, numerical optimization is performed for a variety of scenarios and aimed at increasing the flutter and linear buckling stability margins of tow-steered plates, considering the geometrical parameters defining the fiber trajectories on the layers as design variables. The results obtained for the different optimization scenarios are compared, having a composite plate with unidirectional fibers as the baseline and aimed at evaluating the benefits achieved by the optimum tow-steered plates. The results enable quantification of the stability improvements by exploring fiber steering, which has been shown to be beneficial, even in situations in which manufacturing constraints are accounted for.

© 2019, Springer Nature Switzerland AG.The present paper is devoted to the modeling of systems comprising a flexible rotor mounted onto an elastic base, undergoing arbitrary rotations. By using a Lagrangian approach, the equations of motion are derived for the coupled rotor-base system, considering finite element discretization for both the base and the rotor. Numerical simulations are performed for a specific configuration of the rotor-bearing system and attitude motion. Results are interpreted to evaluate, both qualitatively and quantitatively, the influence of the base motion and flexibility on the dynamic behavior of the rotor, in terms of unbalance responses. Based on the results, conclusions are drawn, especially in terms of the conditions under which the flexibility of the base is indispensable for accurate prediction of the rotor behavior.

© 2018 Elsevier LtdCylindrical bodies subjected to external flow can vibrate due to the fluctuations of the forces induced by vortex shedding. The way these coherent fluid flow structures are formed and how they excite the structure depends on parameters, such as the Reynolds number, the reduced velocity, and the geometry e.g., the proximity of the structure to other bodies. These vibrations change the drag and lift forces by means of a nonlinear interaction. In addition, vibrations can cause crack nucleation and propagation in the structure. This is especially important when oil or natural gas is being transported in pipe-like structures, subjected to waves and sea currents. The present paper aims to characterize the influence of the proximity of the seabed on the fluid–structure interaction, considering horizontal pipes anchored by dunes. The simulations were undertaken for a nominally horizontal, elastic pipeline, 42 m in length and 0.273 m in diameter, with a mid–span static sag of 1.06 m due to self-weight. Seven different distances between the pipeline and the seabed were tested. The structural and fluid-dynamic models were coupled numerically, which allows the simulation and analysis of the flow using a single computational tool. The equations modeling the flow were solved in an Eulerian domain, while the surface of the immersed body was represented by a set of Lagrangian points. The immersed boundary method was used to impose a Dirichlet boundary condition on the Eulerian domain at the boundary between the structure and the fluid. It was also used to determine the fluid dynamic forces acting on the structure. An in-house three-dimensional computational framework was developed to simulate the turbulent incompressible flow subjected to fluid–structure interaction in conjunction with a beam modeled according to Timoshenko's theory. The obtained results are consistent, as expected for this problem.

© 2019 Elsevier Ltd and Techna Group S.r.l.Life expectancy has been growing, and more people are developing bone diseases such as arthritis and osteoporosis. Degenerative pathologies, injuries, and trauma can damage the bone tissues, requiring treatments that facilitate its repair, replacement, or regeneration. In this context, many materials have been developed to match this demand. Bioglasses and ceramics are promising inorganic materials to produce scaffolds for bone regeneration due to their attractive properties, such as biocompatibility, osteoinduction, and osteoconduction, besides their similarity with bone composition. Although their established advantages, these materials present limitations such as inadequate mechanical properties and fast degradation rate. Research work has been widely carried out to develop bioglasses, silicate, and phosphate calcium ceramics scaffolds with appropriated properties to enlarge their applications in bioengineering. Different fabrication techniques have also been evaluated. Incorporating other materials or particles, such as polymers, oxides and metal particles into the scaffolds has shown beneficial effects in mechanical strength and bone production stimulation. In this review, we provide an overview concerning the recent advances in developing calcium phosphates, calcium silicates, bioglasses, and composites scaffolds for bone regeneration in medical and dental applications.

© 2019 Elsevier B.V. The aim of this study was to tailor the deposition parameters of magnetron sputtering to synthetize tantalum oxide (Ta x O y ) films onto commercially pure titanium (cpTi) surface. The structural and optical properties, morphology, roughness, elemental chemical composition and surface energy were assessed. The impact of Ta x O y films on initial Streptococcus sanguinis adhesion was investigated. The morphology and spreading of pre-osteoblastic (MC3T3-E1) cells on a crystalline tantalum oxide film were evaluated. Ta x O y films with estimated thickness of 600 nm and different structures (amorphous or crystalline) were produced depending on the various oxygen flow rates and parameters used. X-ray diffraction analysis revealed that the 8 O 2 sccm (600 °C/400 W) group showed crystallization corresponding to the β-Ta 2 O 5 phase. Optical analysis showed that the 4 O 2 sccm (200 °C 300 W) to 8 O 2 sccm (600 °C 300 W) groups and 10 O 2 sccm (200 °C 300 W) group presented regular and large-amplitude interference oscillations, suggesting high optical homogeneity of the films. The crystalline β-Ta 2 O 5 coating showed higher roughness and surface energy values than the other groups (P <.05) and was biocompatible. Compared with cpTi, the amorphous and crystalline tantalum oxide films did not increase bacterial adhesion (P >.05). By tailoring the deposition parameters, we synthetized a crystalline β-Ta 2 O 5 coating that improved titanium surface properties and positively affected cell spreading and morphology, making it a promising surface treatment for titanium-based implants.

© MDPI AG. All rights reserved.A thermal analysis of a 5 kVA dry-type transformer under linear and non-linear loads conditions is studied in this paper. The main goal here is to calculate the hottest-spot transformer temperature under free convection through the resolution of the heat conduction equation in three dimensions (3D) using COMSOL Multiphysics®. The proposed technique was validated through experimental data obtained in laboratory. The temperature inside the cores was measured under the influence of free convection. The radiation emission was also measured through a thermal camera. The heat transfer coefficient for both conditions was obtained from empirical correlations. The hottest-spot temperatures were determined from the analysis in the commercial software which was used for the numerical simulations of the transformer heating and cooling under some loading conditions. The temperature residuals, that is, the experimental temperature values subtracted by the numerical temperature values, were below 10%. The numerical analysis found that the hottest-spot temperatures in the core reached 20C above the transformer insulation limit. The location of the hottest-spot as well as the obtained temperatures can be used to improve more resistant dry-type transformers.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Aviation system is one of the most complex dynamical systems created. This system is subjected to the occurrence of different failures during flight. Online failure detection and identification (FDI) techniques may allow an aircraft to avoid unrecoverable post failure flight conditions and continue the mission by control laws reconfiguration. This paper focus on presenting the current FDI methods used by the aeronautical industry and by academic and research communities, discussing the gap that exists between these two domains and presenting the challenges and directions to bring them closer in order to improve flight safety.

© 2019 by Xin Ning. Published by the American Institute of Aeronautics and Astronautics, Inc.This paper aims to analyze and compare different machine learning FDI techniques to detect and identify aircraft failures using offline analysis of FDR data. We use a motion-based flight simulator (SIVOR) to perform human-in-the-loop experiments. We performed 2 experiments of a take-off maneuvre under different conditions: normal flights and flights with aircraft failures (flap, engine, aileron and elevator failures). We applied and compared different supervised machine leaning techniques to detect and identify aircraft failures: Decision Trees, Ensemble Classifiers, Support Vector Machines (SVM) and k-Nearest Neighbors (kNN). Boosted Trees algorithm, an Ensemble Classifier, presents the best result regarding overall accuracy for both flight experiments (99.5% and 97.7%).

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work aims at presenting an integrated development system to a motion real-time flight simulator using a robotic device. This flight simulator is called SIVOR (Simulador de Voo Robótico – Robotic Flight Simulator). This is a multidisciplinary project since it involves different systems with different level of complexity, which by itself give some challenges in how to develop this type of flight simulator. In order to have a flight simulator with base motion upon robotic device it is necessary the domain of systems like robotic, pilot modeling, filtering design, here called by washout filter, aeronautic modeling which includes traditional systems as automatic flight control, aerodynamic, propulsion, ground handling, sensors and actuation. Therefore a considerable effort in the development is demanded to have a representative aircraft model been executed in a real-time flight simulator with robotic motion. Thus this paper presents an integrated modeling process to represents all of the system in order to give a more maturity development cycle, in order to reduce the uncertainties presented in the begin of any project and that becomes more challenging for any complex system. The real-time motion flight simulator based upon robotic environment has a nonlinear flight mechanic model of EMBRAER 190-E2, and here won’t be presented in order to protect the intellectual property and compliance policies of EMBRAER S.A., the other systems will be explained in detail and a sensitive analysis is presented in order to demonstrated that an model based approach shall be used in this kind of flight simulator in order to speed up the maturity level of the system.

� 2019 by German Aerospace Center (DLR). Published by the American Institute of Aeronautics and Astronautics, Inc.The need for an optimized aircraft development cycle imposed by market constraints, associated with airliners demands for more cost-effective and safe operations, has become a challenge for aircraft OEM in face of new aircraft ever-growing complexity. Emergent behaviors during the development phase causing project schedule oscillations and delays in the adequate time to market, associated with accident statistics after entering into service phase (especially those associated with Loss of Control in Flight), force new approaches for the development of new aircraft. Based on this scenario, this manuscript describe the efforts to develop a flight simulation-engineering center based on a robotic motion platform. This promising configuration might contribute to overcome some of the previous problems due to augmented motion platform workspace. However, the limited robot payload capacity and the need for a commercial jet representative cockpit, generate critical design constraints and technological challenges to implement this configuration. This manuscript details the design strategy to build the flight simulator assisted by a robotic motion platform and also analyses possible applications.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper presents the SIVOR project, an anthropomorphic-robotic flight simulator under development at the Aeronautics Institute of Technology (ITA), discussing the contribution of an additional 7th degree of freedom (DOF) provided by a linear unit to improve the pilot perception inside the flight simulator. In this context, starting from a canonical washout filter (CWF) implementation, a model-based comparative evaluation – regarding the pilot sensation – is performed considering (i) models of the robotic system with and without the linear unit, (ii) modified versions of the motion-cue algorithm (MCA), (iii) and perception models of the human vestibular system. Such integrated model is used also as the first verification for a predefined flight mission. The results obtained so far suggest an improvement on the representation of the linear acceleration as a larger workspace is provided, though also highlighting the need for further developments on the MCA structure for a better usage of the near feature.

© 2019This paper presents a human factors analysis in aviation within the context of failure detection and identification (FDI) using statistical data analysis and clustering. We used data from experiments in a motion-based flight simulator (SIVOR) with 4 experienced pilots performing a take-off maneuvre under three conditions: normal, under engine failure and under flap failure. We propose two metrics based on statistical data analysis to evaluate and compare human behavior during flight. We also use k-means clustering in order to classify flights according to maneuvre conditions and misclassified flights are further analyzed according to which pilot has performed it. Results show that for the statistical data analysis the behavior of one specific pilot has higher dissimilarity with all other pilots. Moreover, for the k-means clustering, most of the misclassified flights were performed by this same pilot.

© 2019, Journal of Aerospace Technology and Management. All rights reserved.This paper presents a detailed analysis about the implementation of a washout filter on the SIVOR (Simulador de Voo Robótico – Robotic Flight Simulator) project. The main objective of this project is to develop, on an anthropomorphic robot, a flight simulator which can be used as an Engineering Development System (EDS) and a pilot training platform, capable of providing feelings the pilot would only have in more intensive maneuvers, such as losses/gains of G in aircraft flight tests. The SIVOR project also has the objective of providing a cost-efficient and flexible tool that can be used during the design phases of aircrafts. One of the demanded features of such simulator is a representative behavior of its motion system, which is achieved by an adequate implementation of the washout filter. To the best knowledge of the authors, there are no works in the literature that present a detailed discussion about the implementation of a classical washout filter in such flight simulator, especially when the translational channel is used to its limits. Experimental results to support the proposed solutions are presented herein.

© 2018 Elsevier B.V.With the purpose of making the use of model based techniques in industrial software development more efficient, this work proposes the combined application of two verification techniques: model checking with UPPAAL and CoFI (Conformance and Fault Injection) model based testing with ConData. This combination is supported by ConTEA, a software tool for automatically connecting UPPAAL to ConData, and, therefore, explore both techniques simultaneously. We present the tool and discuss the use of ConTEA in two different development processes. The first process investigates how CoFI can contribute to identify gaps in the specification and implicit assumptions made by engineers when applying model checking. The second process focuses on how model checking can improve the development and verification of the models that are used for model based testing. The proposed processes were applied to three case studies. Based on them, we compare the proposed processes to the traditional CoFI and UPPAAL stand-alone processes. The results indicate that the combined use of the two verification technique contributes to the identification of a large range of diversified errors and problems early in the development cycle.

© 2019 IEEE.This work presents the development of the nonlinear 2D Shallow Water Equations (SWE) in polar coordinates as a boundary port controlled Hamiltonian system. A geometric reduction by symmetry is obtained, simplifying the system to one-dimension. The recently developed Partitioned Finite Element Method is applied to semi-discretize the equations, preserving the boundary power-product of both the original 2D and the reduced 1D system. The main advantage of this power-preserving semi-discretization method is that it can be applied using well-established finite element software. In this work, we use FEniCS to solve the variational formulation, including the nonlinearity provided by the non-quadratic Hamiltonian of the SWE. A passive output-feedback controller using damping injection is used to dissipate the water waves.

© 1993-2012 IEEE.In this brief, we develop a mathematical model of a flexible spacecraft system composed of a hub and two symmetrical beams using the port-Hamiltonian framework. This class of system has favorable properties, such as passivity for controller synthesis and stability analysis, where the global Hamiltonian plays the role of a Lyapunov function candidate. The spacecraft model is viewed as a power-conserving interconnection between an infinite (beam) and finite (hub) dimensional system. We show that the interconnection result has a port-Hamiltonian structure and is passive. The introduction of a nonlinear feedback term, which takes into account the beam's flexibility, is developed using the control by an interconnection approach. The closed-loop stability is proven; then, through explicitly solving the partial differential equations of the system, asymptotic stability is obtained. Finally, the experimental results are carried out to assess the validity of the proposed design methodology.

© Universal Technology Corporation, 2018.The development of modern, more efficient transport aircraft and High-Altitude-Long-Endurance (HALE) aircraft requires solutions that involve lightweight structures and high aspect ratio wings for maximum aerodynamic efficiency. However, this may result in flexible wings, such that the coupling between rigid-body and structural modes deteriorates stability and handling qualities of the aircraft. These can be improved by the continuous operation of control systems with the use of structural information, such as wing deformed shape. Strain gages can be used for such an application. However these sensors may have input interference, such as temperature variation, that can cause false strain responses other than the expected measurements due to flight loads. This work presents the analyzes of strain gage measurements due to thermal loads in the X-HALE aircraft wing. Three thermal correction methods were proposed: functions of temperature, dummy gage, and high-pass filtering. Each was tested on indoor and outdoor experiment setup, which uses a lamp and natural temperature variation throughout a full day as heat sources. All methods were effective in removing thermal drift of indoor experiment data. However, only high-pass filtering method was successful in the outdoor experiment. Indoor thermal test results done on the full 4m X-HALE aircraft, with the addition of impact excitations on the aircraft’s wing tip, showed that the high-pass filtering was able to remove thermal drift while maintaining all responses in the frequency range of interest. Therefore, this method is suitable to the present application.

© Universal Technology Corporation, 2018.This paper presents a static iterative aero-structural method applied as a study case to a transport aircraft with wing aspect ratio of 12. It evaluates the structure geometric nonlinearity effect on aerodynamic coefficients. A Nonlinear High-fidelity Static Fluid-structure Iteration tool (E2-FSI) was used in this study case. It combines Reynolds Average Navier Stokes Computational Fluid Dynamics with detailed Finite Elements Method in linear and nonlinear structural analyses. The wing body nonlinear high fidelity static aeroelastic effect on flexible pitching moment coefficient was correlated to rigid tail trimming demand showing static tail loads being modified by wing nonlinear flexibility.

© 2019, Springer Science+Business Media, LLC, part of Springer Nature.The use of materials for aerospace devices, such as rocket nozzles and thermal shields, depends primarily on their thermal and structural characteristics. Ceramic materials and carbon composites have been studied for this purpose. This work measures and investigates the ablation and thermal diffusivity of hybrid matrix composites of carbon–silicon carbide matrix reinforced by carbon fiber (C/C-SiC). Silicon powder was added to a phenolic thermoset matrix with proportions of 5, 10, and 20 %. In addition, the liquid polymer infiltration (LPI) process using a silicone polymer was used to produce the same composites. A thermal plasma torch was used to obtain the ablation and effective thermal diffusivity characteristics of the materials. The morphologies, microstructures, and chemical compositions of the samples were investigated by scanning electron microscopy and energy-dispersive spectrometry (SEM/EDS) and X-ray diffraction (XRD). The thermal diffusivities of the composites were found to be in the range of 0.2–1.5 × 10−6 m2·s−1 from 700 °C to 1000 °C, respectively. The void volume fraction of the composites was approximately 20 % and decreased the thermal diffusivity.

© 2019 IOP Publishing Ltd.Organic contaminants (for example in wastewater effluents) cause serious health and environmental problems due to their high chemical oxygen demand (COD), low biodegradability, and toxicity. Non-equilibrium and thermal plasmas were actively studied and numerous reactor geometries were developed to induce chemical reactions in treated liquids. Thermal plasma, because of its elevated temperatures and presence of highly active radicals, accelerates kinetics of chemical reactions and achieve high destruction efficiencies in processing of gaseous, liquids and solid materials. In this work, a plasma-chemical reactor, with submerged plasma jet for treatment of liquid residues, is presented and applied for treatment of water contaminated with glycerine. A distinctive feature of submerged plasma treatment is the high local plasma temperature and low treated liquid temperature, which promotes high quenching rate that preserves radical concentration and promotes advanced oxidation of aqueous effluents in highly turbulence flow. This work presents the main functioning characteristics of the reactor and the effect of specific energy input on glycerine degradation by thermal plasma.

© 2019, Springer Nature Switzerland AG.Titanate nanorod synthesis method is extremely important due to their large application in electronic, catalysis, and biological areas. However, works reporting the influence of synthesis parameters on the structure, morphology, and properties of titanate nanorods are still rare. Therefore, this work aims to analyze the preparation of titanate nanorods from TiO2 nanoparticles via hydrothermal reaction. The microstructure and morphological properties were evaluated as a function of time, temperature and precursor nature (anatase or anatase/rutile mixture) by X-ray powder diffraction, Raman spectroscopy, transmission electron microscopy and field-emission scanning electron microscopy. The crystallinity of the precursor was the main parameter for the titanate nanorods formation. Besides, temperature has also a direct influence in the fibril morphology. The use of low temperature and anatase/rutile mixture was not able to produce titanate nanorods. Only the use of higher temperatures and pure anatase resulted in rod-like titanates, which showed higher methylene blue photodegradation efficiency than TiO2 nanoparticles.

© 2018 IOP Publishing Ltd.Candida spp are present in 70%-90% of invasive infections and non-thermal plasmas operated at atmospheric pressure have been gaining attention as a new antimicrobial strategy for medical devices. This work presents studies on the inactivation efficacy of biofilms of Candida albicans grown in polyurethane (PU), main constituent of central venous catheter, by atmospheric gliding arc plasma jet operated at different process parameters: gas chemistry/flow(argon, helium, or its mixture with air) and plasma pulsing. The investigation was performed in the post-discharge region of the plasma jet. After plasma treatment, the colony-forming units(CFU)were counted, and the chemical bonding (FT-IR) and morphological (SEM) analyses of the surface of the biofilm plus PU substrate were investigated. Furthermore, optical emission spectroscopy (OES) technique was applied to characterize the plasma chemistry and measure the OH concentration and rotational temperature, together with thermal analyses of the substrate during treatment. CFU results showed that gliding arc plasma jet was efficient for the inactivation of C. albicans biofilms. It obtained a maximum CFU reduction of 100% and 98% for 4 L min-1 air/6 L min-1 He and 99% and 98% for 4 L min-1 air/6 L min-1 Ar in continuous and pulsed mode, respectively. SEM and FT-IR analyses corroborate with results of % CFU reduction, showing a reduction of the biofilm constituents on the substrate surface. From OES and substrate thermal analyses, it was possible to verify that, although the OH concentration and rotational temperature of air/He plasma jet are lower in comparison to the air/Ar, a drastic increase of the substrate temperature during the treatment (up to 70 °C)was observed for this plasma chemistry.

© 2019 Elsevier Ltd and Techna Group S.r.l.Life expectancy has been growing, and more people are developing bone diseases such as arthritis and osteoporosis. Degenerative pathologies, injuries, and trauma can damage the bone tissues, requiring treatments that facilitate its repair, replacement, or regeneration. In this context, many materials have been developed to match this demand. Bioglasses and ceramics are promising inorganic materials to produce scaffolds for bone regeneration due to their attractive properties, such as biocompatibility, osteoinduction, and osteoconduction, besides their similarity with bone composition. Although their established advantages, these materials present limitations such as inadequate mechanical properties and fast degradation rate. Research work has been widely carried out to develop bioglasses, silicate, and phosphate calcium ceramics scaffolds with appropriated properties to enlarge their applications in bioengineering. Different fabrication techniques have also been evaluated. Incorporating other materials or particles, such as polymers, oxides and metal particles into the scaffolds has shown beneficial effects in mechanical strength and bone production stimulation. In this review, we provide an overview concerning the recent advances in developing calcium phosphates, calcium silicates, bioglasses, and composites scaffolds for bone regeneration in medical and dental applications.

© 2019, Springer Nature Switzerland AG.Silver vanadate, especially β-AgVO3, have a wide range of technological applications due to remarkable biological, optical, and electrical features. The structure, morphology, and properties of β-AgVO3 are directly affected by synthesis conditions. A comparative study between two different synthesis routes (precipitation and hydrothermal) of β-AgVO3 was systematically investigated in this work. X-ray diffraction, Raman spectroscopy, scanning electron microscopy, zeta potential, and UV–visible spectrometry results showed that the hydrothermal method produced more homogeneous samples of β-AgVO3, with elevated purity and crystallinity. In addition, the sample of β-AgVO3 obtained by hydrothermal method had a wire-like morphology while that obtained by precipitation had irregular shape. Finally, the hydrothermal procedure showed more elevated reproducibility.

© 2019, Springer Nature Switzerland AG.Abstract: The improvement of compatibility between carbon nanotubes (CNTs) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was achieved using CNT functionalized with γ-aminobutyric acid (GABA). The efficiency of the CNT functionalization with GABA was evaluated by X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (FT-IR), Raman spectroscopy, and transmission electron microscopy (TEM). The PHBV/CNT nanocomposites were produced in the molten state with the addition of 0.5 wt% of CNT (pristine, oxidized and functionalized with GABA) and characterized concerning the Izod impact strength tests. The impact fracture morphologies were analyzed using scanning electron microscopy. The results showed that GABA was covalently attached to CNT, resulting in the detection of nitrogen in the XPS survey, the shift of carbonyl peak wavelength on FT-IR, and a higher degree of structural disorder, detected by Raman and observed in TEM images. The impact strength was not significantly affected by the introduction of CNT; however, the impact fracture mechanism was changed from fragile to ductile when CNT was functionalized with GABA. These results are promising for the production of environmentally friendly nanocomposites with superior properties. Graphic abstract: [Figure not available: see fulltext.]

© 2019, Springer Nature B.V.This study aimed to evaluate the effects of cold atmospheric pressure plasma (CAPP) jet on Trichophyton rubrum growth, germination and adherence to nail. The effects of plasma jet on T. rubrum conidia germination and on mycelial growth were evaluated by in vitro assays. An ex vivo nail infection model was used to evaluate the effects on conidia adherence and infection. Biochemical analyses of nail fragments exposed or not to CAPP were performed by attenuated total reflectance–Fourier transform infrared (ATR–FTIR) spectroscopy. Plasma jet exposure for 10 and 15 min completely inhibited mycelial growth after only one exposure. Fifteen minutes of exposure could reduce conidia germination in suspension. Fungal suspensions exposed to plasma jet for 10 and 15 min were not able to infect nail specimens. These results were corroborated by ATR–FTIR analyses of nail fragments. In conclusion, single exposure to CAPP for 15 min was able to inhibit fungal growth, adherence and infection capacity. The results suggest that cold atmospheric plasma jet can be a promising alternative for the treatment of onychomycoses caused by T. rubrum.

© 2019 Elsevier LtdSuper hydrophilic scaffolds of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) with 3 wt % of acetylated (CNC-Ac) and PEGylated (CNC-PEG) cellulose nanocrystals (CNC) were prepared. PHBV, PHBV/CNC-Ac, and PHBV/CNC-PEG scaffolds were characterized with respect to their morphology by scanning electron microscopy (SEM) and X-ray microtomography. The crystallinity was evaluated by differential scanning calorimetry (DSC) and the mechanical properties by uniaxial compression tests. The presence of residual solvent was identified by gas chromatography (GC), wettability measured by static contact angle and aqueous adsorption by gravimetry. All the scaffolds showed porous morphology, being that, for neat PHBV the morphology was more regular with oriented pores. The porosity was reduced by 26% with the introduction of CNC-Ac and CNC-PEG, and the compression modulus increased by 25% and 72% for PHBV/CNC-Ac and PHBV/CNC-PEG scaffolds, respectively, compared to neat PHBV. Even with lower porosities, PHBV/CNC-Ac and PHBV/CNC-PEG adsorbed 16% and 67% more water than PHBV scaffold, following the intraparticle diffusion model for all the samples. No residual solvents were found and the crystallinity was slightly increased upon addition of CNC-Ac and CNC-PEG. Therefore, the addition of CNC-Ac and CNC-PEG can improve both compressive modulus and water uptake, turning PHBV nanocomposite scaffolds suitable for tissue engineering applications.

© 2019 IOP Publishing Ltd.In this work, a new strategy of carbon nanotubes (CNT) pre-dispersion (PD) in acetone to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/CNT nanocomposites was evaluated. PHBV/CNT nanocomposites were produced in the molten state with the addition of 0.5 wt% of CNT and evaluated by scanning electron microscopy with field emission gun (FEG-SEM), differential scanning calorimetry (DSC), Izod impact tests, nanohardness, and x-ray diffraction (XRD). FEG-SEM showed well-dispersed CNT for sample subjected to pre-dispersion (PHBV/CNT-PD), and DSC showed a reduction in the degree of crystallinity from 62% to neat PHBV to 55% for PHBV/CNT-PD. Impact resistance was positively affected by the pre-dispersion, and nanohardness showed more homogeneous values for PHBV/CNT-PD sample compared to PHBV/CNT (without pre-dispersion). XRD proved that hot pressing affects plans orientation, and so does the addition of CNT into PHBV. The CNT dispersion into PHBV analyzed by the ratio between planes area showed that PHBV/CNT-PD sample had homogeneously dispersed CNT.

© 2019, Springer Nature Switzerland AG.Titanate nanorod synthesis method is extremely important due to their large application in electronic, catalysis, and biological areas. However, works reporting the influence of synthesis parameters on the structure, morphology, and properties of titanate nanorods are still rare. Therefore, this work aims to analyze the preparation of titanate nanorods from TiO2 nanoparticles via hydrothermal reaction. The microstructure and morphological properties were evaluated as a function of time, temperature and precursor nature (anatase or anatase/rutile mixture) by X-ray powder diffraction, Raman spectroscopy, transmission electron microscopy and field-emission scanning electron microscopy. The crystallinity of the precursor was the main parameter for the titanate nanorods formation. Besides, temperature has also a direct influence in the fibril morphology. The use of low temperature and anatase/rutile mixture was not able to produce titanate nanorods. Only the use of higher temperatures and pure anatase resulted in rod-like titanates, which showed higher methylene blue photodegradation efficiency than TiO2 nanoparticles.

© 2018 Elsevier Ltd and Techna Group S.r.l.This paper reports the development of new ZnO/carbon xerogel composites (XZn w) for photocatalytic applications. The use of black wattle tannin as a precursor to the carbon xerogel aimed at reducing costs and environmental impacts. The composites were characterized by diffuse reflectance spectroscopy (DRS), BET surface area, scanning electron microscopy (FEG-SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and X-ray diffraction (XRD). The photocatalytic performance of the materials was evaluated in the decomposition process of methylene blue, a known toxic pollutant. The impacts of the catalyst dosage and calcination temperature on the photocatalytic process were also examined systematically. The X-ray profiles of the XZn w evidenced the existence of the hexagonal structure of the zinc oxide (wurtzite) in the composites. The XPS and XRD analyses confirmed the incorporation of carbon in the zinc oxide crystalline structure. The higher carbon content resulted in a larger surface area. All composites presented the ability to absorb radiation in less energetic wavelengths, contrary to pure zinc oxide that only absorbs radiation of wavelengths below 420 nm. The optimal dosage and calcination temperature were found to be 0.2 g L−1 and 300 °C. All the developed composites displayed significant photocatalytic activities in the decomposition of methylene blue under both visible and solar light. The composites had superior photocatalytic efficiency under visible light when compared to pure zinc oxide. The XZn 0.5 presented the best degradation efficiency under visible radiation. All materials presented similar photocatalytic responses under solar light, evidencing the synergy between the carbon xerogel and the zinc oxide. The photocatalytic mechanism was evaluated by trapping experiments to be mainly controlled by the electron vacancies that are generated during the photoexcitation of the composites.

© 2019 by the authors.Behavior studies of thermoplastic polymers during non-isothermal crystallization are extremely important since most of their properties are influenced by degree of crystallinity and the crystallization process. In general, an approach based on a model-fitting method is used to perform crystallization kinetic studies. Due to their inability to uniquely determine the reaction mode, many studies have used the isoconversional method, where it is not necessary to assume a crystallization model to obtain the kinetic parameters. Therefore, in this work, the influence of acid and octadecylamine functionalized carbon nanotubes (CNTs) in the crystallization kinetic of polyethylene (PE) was studied using an isoconversional method with differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The kinetic parameters and the crystallization model were determined. The incorporation of functionalized and non-functionalized CNTs into PE did not change the Johnson-Mehl-Avrami crystallization model. However, the CNTs increased the crystallization temperature and reduced the activation energy for crystallization. In addition, the Avrami coefficient values were lower for the nanocomposites when compared to pure PE. The incorporation of CNTs accelerated the crystallization of PE, reducing the crystallite sizes and modifying their morphology.

© 2019 by the authors. Licensee MDPI, Basel, Switzerland.Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a widely studied polymer and it has been found that porous PHBV materials are suitable for substrates for cell cultures. A crucial factor for scaffolds designed for tissue engineering is the water uptake. This property influences the transport of water and nutrients into the scaffold, which promotes cell growth. PHBV has significant hydrophobicity, which can harm the production of cells. Thus, the addition of α-wollastonite (WOL) can modify the PHBV scaffold’s water uptake. To our knowledge, a kinetics study of water uptake of α-wollastonite phase powder and the PHBV matrix has not been reported. In this work, PHBV and WOL, (PHBV/WOL) films were produced with 0, 5, 10, and 20 wt % of WOL. Films were characterized, and the best concentrations were chosen to produce PHBV/WOL scaffolds. The addition of WOL in concentrations up to 10 wt % increased the cell viability of the films. MTT analysis showed that PHBV/5%WOL and PHBV/10%WOL obtained cell viability of 80% and 98%, respectively. Therefore, scaffolds with 0, 5 and 10 wt % of WOL were fabricated by thermally induced phase separation (TIPS). Scaffolds were characterized with respect to morphology and water uptake in assay for 65 days. The scaffold with 10 wt % of WOL absorbed 44.1% more water than neat PHBV scaffold, and also presented a different kinetic mechanism when compared to other samples. Accordingly, PHBV/WOL scaffolds were shown to be potential candidates for biological applications.

© 2019 Vinícius D. N. Bezzon et al.A brief review reporting the recent advances on the carbon nanostructured materials-based sensors covering recently published works is presented. Several works dealing with experimental and theoretical data are reviewed and discussed. The main results for carbon nanotubes, nanodiamonds, fullerene, graphene, and hybrid carbon-nanostructured devices that show sensing properties in different fields were considered for the discussions. The goal of this paper was to highlight sensor mechanisms, and the best results reached up to now are creating bases for further applications.

© 2019 The Royal Society of Chemistry.Carbon nanotubes (CNTs) have remarkable mechanical, thermal, electronic, and biological properties due to their particular atomic structure made of graphene sheets that are rolled into cylindrical tubes. Due to their outstanding properties, CNTs have been used in several technological fields. Currently, the most prominent research area of CNTs focuses on biomedical applications, using these materials to produce hybrid biosensors, drug delivery systems, and high performance composites for implants. Although a great number of research studies have already shown the advantages of CNT-based biomedical devices, their clinical use for in vivo application has not been consummated. Concerns related to their toxicity, biosafety, and biodegradation still remain. The effect of CNTs on the human body and the ecosystem is not well established, especially due to the lack of standardization of toxicological tests, which generate contradictions in the results. CNTs' toxicity must be clarified to enable the medical use of these exceptional materials in the near future. In this review, we summarize recent advances in developing biosensors, drug delivery systems, and implants using CNTs as smart biomaterials to identify pathogens, load/deliver drugs and enhance the mechanical and antimicrobial performance of implants.

© 2019 Elsevier Ltd and IIRThe use of hydrocarbons as refrigerants has increased substantially in the past decades due to more severe regulations on direct and indirect carbon dioxide emissions. However, safety standards related to flammable fluids limit the amount of propane (R-290) used in air-conditioning (AC) systems. In this study, an experimentally validated numerical model for a split-type AC system is employed and, for the first time, an air-side peripheral fin geometry is used in the condenser in an attempt to reduce the refrigerant charge for a given system cooling capacity. To establish a fair basis for comparison, plain, wavy and louvered fins were also investigated in the model. A more realistic assessment of the system performance was achieved by considering the POE ISO 22 oil circulation ratio (OCR) in the computation of the physical properties of the mixture. The results have shown that, for the simulated range, heat exchangers with peripheral fins provided higher values of thermal conductance (UA) and cooling capacity than other types of fins. A substantial decrease in the R-290 mass (as high as 12.13%) was observed when peripheral fin condensers were employed.

© 2019 Elsevier LtdThe research and technological development towards compact energy conversion systems for space applications allow the emergence of new mission possibilities, especially those directed for deep space explorations. Besides the final efficiency, the most crucial factor of an energy conversion system for nuclear propulsion purposes is the total mass and size of the system. Considering the Closed Brayton Cycle (CBC) as the energy conversion system for a nuclear power system, a numerical analysis was carried out in order to predict the thermal performance of cold side of the system (i.e., heat pipes and radiator) for initial design purposes. The complete space heat pipe-radiator array was discretized in control volumes where a variation of geometrical parameters was included, resulting in a stepped trapezoidal-shaped radiator (RAD) as output. The heat capacity was limited by the geometry of each panel section, being its heat pipe modeled to fit the given geometry and verified against operational limits. The proposed design-based model considered a physical and thermal coupling with temperature drops along the heat pipe (HP) axial direction, the radiator panel surface, and the cold heat exchanger duct, providing reasonable global parameters to aid the design considering mass and size optimization of a heat pipe-radiator assembly. The number of heat pipes and the total heat pipe-radiator assembly mass and length were evaluated for different heat pipe spacing, heat transfer rate, cold heat exchanger (CHE) inlet temperatures, and radiation shield shadow angles. It was observed a point of minimum HP-RAD mass and length when the heat pipe spacing and CHE inlet temperature are varied, for a given heat transfer rate and shadow angle.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering.Heat transfer processes using two-phase boiling flows are often found in the industry, due to the high-efficiency heat removal, with a minimum difference of temperature between the heated surface and fluid. Moreover, the use of computational fluid dynamics to solve safety issues related to nuclear reactors has increased rapidly, but a complete validation is still being carried out. Therefore, this study aims the assessment of different sub-models of the interfacial heat transfer coefficient which is used as a closure relation in the two-fluid multiphase model. As a manner to validate the numerical results, the set of experimental conditions of Bartolomei and Chanturiya (Therm Eng 14:123–128, 1967) were applied to an upwards flow in a circular channel, under high water saturation pressures. The interfacial sub-models were implemented into an axisymmetric simulation domain, using the Eulerian two-fluid approach. Three different saturation pressures and two uniform heat fluxes were considered in the simulation runs. Fixed mass flux and subcooled degree of 900 kg/m2 and 60 K were applied, respectively. A satisfactory agreement was achieved for the estimation of the heated wall temperature, the liquid bulk temperature and the onset of saturated boiling. Different heat transfer closure relations promoted different vapor volume fraction along the channel, indicating the importance of an adequate interfacial heat transfer correlation to predict the flow boiling phenomena.

© The Authors, published by EDP Sciences, 2019.Current energy conversion machines such as the micro gas turbine can be improved by harvesting the low-grade energy of the exhaust. A prominent option for such is the organic Rankine cycle due to its relatively efficient and reliable design. This manuscript presents a review on the subject and is the first step toward the design of an organic Rankine cycle bottoming a 100 kWe recuperated gas turbine. After introducing and covering the historical development of the technology, appropriate guidelines for defining the cycle arrangement and selecting the fluid are presented. At last, the viability of the cycle is assessed by assuming an appropriate efficiency value and general cost functions. The organic Rankine is expected to generate an additional 16.6 kWe of power, increasing the electrical efficiency from 30 to 35%. However, the capital cost increase was estimated in 48%.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work presents and analyzes the suitability of using differential GPS equipment (DGPS) for the determination of air data system errors by means of flight testing of the H-50 (AS 350) helicopter. Since the Pitot-error cannot be undervalued, two existing methodologies that use the DGPS as a data acquisition tool have been adapted for the usage in helicopters. Results of flight tests using a validated technique (tower flyby and ground speed course) are presented for the purpose of comparison with data obtained from both proposed techniques. Data are processed through mathematical equations and specific code in MatLab® platform, which has been adapted specifically for this research. Two methodologies using DGPS are set: the first needs three stabilized legs for each speed within the desired flight envelope whose trajectory describes a path similar to a clover leaf, which suggests the method's name: "cloverleaf"; The second uses acceleration and deceleration in 90 degrees alternated legs forming a windbox-like design. The data reduction is performed by iterations of the estimated parameters until a convergence criterion is reached using the analysis of the outputs. Results show the suitability of both proposed methods from a quantitative point of view. Qualitatively, the windbox maneuver with parameters estimation from the analysis of output-error allows reducing material resources expenditures without quality degradation.

© 2019, Avestia Publishing.In an effort to ensure the robustness and numerical stability of a three-dimensional explicit compressible code for all speed flows, a preconditioning technique was implemented. The code solves Euler steady-state equations into a three-dimensional flow. Local preconditioning was implemented due to their accuracy in predicting lift and drag forces on mixed flows. However, for low speed flows near stagnation points numerical perturbations are amplified, generating a loss in the convergence rate, code accuracy and robustness. Aiming to improve the preconditioning accuracy and convergence rate suggested a new limit to the preconditioning sensor based on the flow pressure. Numerical simulations of a subsonic flow over a cylinder showed a faster convergence rate when the preconditioning technique was implemented.

© 2019, Avestia Publishing.In this paper are presented a preconditioning technique to be implemented in a three-dimensional explicit compressible code to solve a turbulence flow to steady state regime. A local preconditioning technique with accurate predictions of mixed speed regimes is implemented in the original code, however, for low flow Mach numbers in the boundary layer region the numerical accuracy is lost to the preconditioning code. To improve the numerical solution are suggested a new limit to the preconditioning sensor based on a pressure sensor and is established an explicit flux function to evaluate the preconditioning sensor in the cell fluxes. The preconditioning code is validated for a supersonic case in nozzle and then to a subsonic case is studied the convergence rate for a low Mach number flow. Numerical solutions demonstrated that the changes applied in the original code improves the accuracy and robustness of the code for low speed flows.

© 2019, Avestia Publishing.A computational program used to calculate the preliminary design of axial turbines which uses the Kacker and Okapuu's loss model was modified to improve the losses predictions implementing Tournier and El-Genk's loss model. The in-house program was written in FORTRAN 90 and is based on the meanline technique to calculate the axial turbine. As the losses interfere in the geometrical calculations applying more accurate loss models, the predictions of the preliminary design are more reliable. The program was applied to design a single-stage turbine and the results are compared with the commercial turbomachine design software AXIALTM®. The improvements obtained by applying a more recent loss model have been discussed as the future works to improve the in-house program.

© 2019 Inderscience Enterprises Ltd.This manuscript provides an exergy-based parallel between combined- A nd steam-cycle power plant configurations burning blast furnace gas (BFG). The combined cycle (CC) was based on a currently operational power plant located in Rio de Janeiro, Brazil. The steam cycle (SC) was created by replacing the gas turbines (GTs) for steam generators (SGs) that handled the same amount of fuel. The results show that the combined cycle achieved 21.25% higher exergy efficiency, although emitting twice as much nitrogen oxide. The combined cycle generated 52.08% less steam while wasting 78.86% less exergy, which indicated that steam generators benefit from a higher amount of excess air. The gas turbine combustion chamber high exergy efficiency indicates that burning low-grade fuels is beneficial for reducing the intrinsic waste of chemical reactions. However, the compression process required prior to combustion undermines this benefit. Ultimately, this manuscript provides a comparison between two options to avail blast furnace gas.

© The Royal Society of Chemistry 2019.A major challenge exists in the preparation of scaffolds for bone regeneration, namely, achieving simultaneously bioactivity, biocompatibility, mechanical performance and simple manufacturing. Here, cellulose nanofibrils (CNF) are introduced for the preparation of scaffolds taking advantage of their biocompatibility and ability to form strong 3D porous networks from aqueous suspensions. CNF are made bioactive for bone formation through a simple and scalable strategy that achieves highly interconnected 3D networks. The resultant materials optimally combine morphological and mechanical features and facilitate hydroxyapatite formation while releasing essential ions for in vivo bone repair. The porosity and roughness of the scaffolds favor several cell functions while the ions act in the expression of genes associated with cell differentiation. Ion release is found critical to enhance the production of the bone morphogenetic protein 2 (BMP-2) from cells within the fractured area, thus accelerating the in vivo bone repair. Systemic biocompatibility indicates no negative effects on vital organs such as the liver and kidneys. The results pave the way towards a facile preparation of advanced, high performance CNF-based scaffolds for bone tissue engineering.

© 2019 Elsevier LtdThe ternary membrane-forming system based on the silk fibroin (SF), glycerol (GLY) and sol-gel precursor of 58S bioactive glass (BG) was studied for the preparation of novel and multifunctional hybrid membranes. The morphology of membranes was observed by scanning electron microscopy (SEM) and spectral imaging, by X-ray mapping technique, were performed in order to investigate the chemical homogeneity of elements. The results show that there is a critical limit for the concentration of GLY and BG for formation of flexible membranes and without a phase separation. XRD and FTIR data showed that the GLY and BG in the silk matrix modifies the short- and intermediate-range order resulting in changes in the silk conformation, i.e., SF molecules are gradually transformed from random coils toward more stable structures – Silk I and Silk II (β-sheets). The solubility study showed that the hybrid membranes have an excellent chemical stability, confirming that the incorporation of inorganic species in the matrix allowed the preparation of novel well-controlled water-soluble membranes. The release profiles of Ca, P and Si confirmed ability of hybrid membranes to deliver controlled inorganic species, which in critical concentration, control the gene expression of osteoblasts and influences cell metabolism and function.

© 2018 Elsevier B.V.In this research, the mechanism of an efficient strategy for the synthesis of 58S bioglass with high structural homogeneity by a citric acid assisted sol-gel route was investigated. This is an interesting approach to prepare bioactive glass via the sol-gel method with application potential in bone tissue engineering and also for the development of new biomedical devices. Herein, 58S bioglass was synthesized by two routes: conventional sol-gel method (CSG) and citric acid assisted sol-gel route coupled to the self-propagating combustion method (SPC). The effects of citric acid on the temperature required for 58S vitreous consolidation, long- and short-range ordering were investigated by several analysis techniques. Results suggested that citric acid molecules serve as an effective molecular template formed by molecular network raised from intermolecular forces, especially the hydrogen bonds, resulting from the chemical interactions between the COOH and hydroxyl groups (water, ethanol, P–OH, Si–OH). In this scenario, citric acid controls the phase segregation during the drying and combustion steps of the gel in the SPC method by establishing chemical interactions (hydrogen bonds) with the superficial silanol groups present on the small-sized silica nanoparticles present in the sol governing their growth. Besides these mentioned features, the self-propagating combustion behavior exhibited by the nitrate-citrate in the SPC xerogel during the combustion step allowed the removal of the organic load and the consolidation of the vitreous structure at a temperature considerably lower than the sample obtained by the CSG method. Consequently, the SPC method leads to the formation of a glass structure with high homogeneity for the 58S, whereas the conventional sol-gel method produces a matrix enriched with calcium phosphate crystalline nuclei - glass-ceramic.

© 2019 Elsevier LtdIn the present research, the microstructure and oxidation behavior of an Fe-8.26Mn-5.25Si-12.80Cr-5.81Ni-11.84Co shape memory stainless steel (SMSS) was studied at 800 °C in air for up to 120 h. Phase changes and oxidation mechanism were discussed based on microscopy analyses, thermogravimetric measurements and thermodynamic simulations. The results show that oxidation exposure promotes the formation of the σ, χ and ferrite phases in the metallic substrate. The oxidation behavior follows a parabolic law, with the kinetics of oxidation being controlled by the Mn2O3 oxide growth in the first hours, and by Mn3O4 and MnCr2O4 spinel growth after 24 h of exposure.

© 2018 Elsevier B.V.TWIP steel weld spots were produced by varying the following welding parameters: welding current, welding time and electrode clamping force. Hardness distributions along the weld spots cross section were obtained by Vickers microindentations. The mechanical strength and failure modes of the weld spots were assessed by tensile-shear tests. Weibull statistics was applied to statistically analyse the data from tensile-shear loading. The results highlighted the influence of welding parameters variations on the Vickers hardness and residual stress state. These properties have a positive correlation to the failure modes and so the mechanical reliability of the weld spots. Welds that failed in pullout mode and partial-interfacial failure mode have statistically higher load bearing capacity than those in interfacial failure mode. The combination of a welding current of 8 kA with a welding time of 16 cycles and an electrode clamping force of 2 kN showed to be the optimum parameters for the investigated TWIP steel weld spots. By using this optimum setup, it was possible to supress interfacial failure mode and to obtain pullout as the predominant failure mode, considerably increasing the mechanical reliability of the weld spots.

© 2019, Latin American Applied Research.In this work, samples of the alloy (composed of 50.9% at Ni) were machined and solubilized so all had the same condition for the hot tensile test between the temperatures 350-650 °C. The results showed that yield stress was between 800 and 597.1 MPa and area reduction between 17 and 75% during the hot tensile test in the respective temperatures. The test at 350 °C shows a fragile fracture characteristic verified by the presence of "river marks", which are characteristic of this type of fracture, because this condition does not promote much plastic deformation. At the other temperatures ductile fracture was observed, with "dimples" that also characterize this type of fracture. This work shows the temperature relationship in the mechanical properties, more specifically the hot tensile test, in NiTi alloy.

© 2019 Sociedade Brasileira de Quimica. All rights reserved.This work aims to determine the kinetic parameters of the thermal decomposition of a lubricating grease based on perfluoropolyether (PFPE) and the computational simulation of this decomposition. The determination of kinetic parameters of thermal decomposition was done by thermal analysis using thermogravimetry (TG) at different heating rates (β) of 10, 15 and 20 °C min-1. With the TG curves obtained, the kinetic parameters were determined by the kinetics methods of Goldfarb et al. and Duvvuri et al., Flynn-Wall-Ozawa and Kissinger. The activation energy of the thermal decomposition of the PFPE grease in the kinect models ranged from 63.54 to 112.3 kJ mol-1. The results of the thermogravimetry indicated that the PFPE grease is thermally stable up to 300 °C. A simulation of the thermal decomposition of the PFPE oil base was carried out by molecular dynamics simulation, using LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) in a temperature range of 0 to 3500 K during 50 ps. The value of the activation energy in the simulation was 92 kJ mol-1. The results show that PFPE oil base and PFPE lubricant grease can be used in high-temperature applications.

© 2019 Sociedade Brasileira de Quimica. All Rights Reserved.Density, viscosity and calorific values are important physical properties to affect the utilization of biofuel. In this work, mixtures of farnesane and a “jet fuel”, QAv-1, were used to study the variation of density and kinematic viscosity as a function of the volumetric fraction of farnesane and temperature. Experimental measurements were carried out for nineteen farnesane blends and pure farnesane and QAv-1, at four temperatures in the range of 293 - 323 K. Variation of high heating (HHV) and low heating (LHV) values were also determined for different blends of farnesane/QAv-1. Several empirical correlations were used to predict the density, the kinematic viscosity, HHV and LHV values. By using some of these empirical correlations, the estimated values of those three properties studied are in excellent agreement with the experimental data, with low absolute average prediction error.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering. This paper presents a study about injectors, where the radial injector was evaluated. This type of injector was chosen because only a small amount of information on it was found. Thus, the radial injector will be compared with other two types of injectors, the orifice plate and the swirl, in terms of parameters, such as discharge coefficient (C d ), regression rate r, and specific impulse (I sp ). In respect of the regression rate, the values appeared increasingly with the test pressure and, consequently, with the injection pressure. Thus, each injector model responded in the same way as for the regression rate behavior; however, the same behavior was not observed in relation to the specific impulse.

© 2019 Elsevier B.V.A computer program was employed to reconstruct the parent microstructure from electron backscatter diffraction maps taken from martensite. The reconstruction is based on a given user-selected orientation relationship. Two reduced-activation ferritic-martensitic Eurofer steels were austenitized for several times and cooled down at different rates. Two parameters are proposed to assess the quality of the reconstruction: the relative frequency of orientations in a determined sub-portion of the Euler space and the distribution of the angular deviation from a given theoretical orientation relationship. The number of active martensitic orientation variants during the transformation depends on grain size. Coarser grains enable a greater number of active variants improving the reconstruction quality. The distributions of angular deviations reveal that the Greninger-Troiano orientation relationship is the one that best describes the martensitic transformation in both steel grades.

© 2019 Universidade Federal de Sao Carlos. All rights reserved.Equal channel angular pressing (ECAP) is one of the severe plastic deformation processes that can also be used for metallic powder consolidation. Consolidation of blended elemental powders of iron, chromium, nickel, and manganese (Fe-25Cr-20Ni-2Mn wt. %) was performed at room temperature in a Φ= 120° die by 1 and 2 passes. SEM micrographs indicated that single pass ECAP consolidated sample presented close to full densification. Additional pass of ECAP led to hardness increase and to an apparent better mixing between the different particles. SEM/EDX analysis made before and after heat treatment of the samples showed that effective diffusion only took place after heat treatment and especially in the sample subjected to 2 ECAP passes. Results indicate that alloying by ECAP consolidation and posterior heat treatment is feasible, especially for systems that cannot be processed by conventional means, as well as mechanical alloying.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering.Worldwide air traffic has been increasing through the last years, and recent researches indicate that the demand for new aircraft will continue to rise over next few decades. Even today, aeronautical manufacturing involves a large proportion of manual labour which directly affects the production capacity of the industry. Thus, in order to meet the market demand and reach the dynamism that the industry must have to compensate the changes that are driven by customers, the automation of the production lines has become increasingly necessary to guarantee the competitiveness of the aircraft manufacturing companies. On this context, this work presents the development of a Design for Automation designing tool—DFAut—that aims at clarifying the automation requirements of a product at the conceptual design phase. Through this study, it has been verified that the use of the DFAut method has yielded automation requirements that were not feasible to be accomplished by a competitive product to the market. However, within the Integrated Product Design concept, the DFAut results could be adjusted to render the product automation configuration feasible. The DFAut tool has been successfully applied to the design of a wing box, and the results are fully discussed herein.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work aims at presenting an integrated development system to a motion real-time flight simulator using a robotic device. This flight simulator is called SIVOR (Simulador de Voo Robótico – Robotic Flight Simulator). This is a multidisciplinary project since it involves different systems with different level of complexity, which by itself give some challenges in how to develop this type of flight simulator. In order to have a flight simulator with base motion upon robotic device it is necessary the domain of systems like robotic, pilot modeling, filtering design, here called by washout filter, aeronautic modeling which includes traditional systems as automatic flight control, aerodynamic, propulsion, ground handling, sensors and actuation. Therefore a considerable effort in the development is demanded to have a representative aircraft model been executed in a real-time flight simulator with robotic motion. Thus this paper presents an integrated modeling process to represents all of the system in order to give a more maturity development cycle, in order to reduce the uncertainties presented in the begin of any project and that becomes more challenging for any complex system. The real-time motion flight simulator based upon robotic environment has a nonlinear flight mechanic model of EMBRAER 190-E2, and here won’t be presented in order to protect the intellectual property and compliance policies of EMBRAER S.A., the other systems will be explained in detail and a sensitive analysis is presented in order to demonstrated that an model based approach shall be used in this kind of flight simulator in order to speed up the maturity level of the system.

� 2019 by German Aerospace Center (DLR). Published by the American Institute of Aeronautics and Astronautics, Inc.The need for an optimized aircraft development cycle imposed by market constraints, associated with airliners demands for more cost-effective and safe operations, has become a challenge for aircraft OEM in face of new aircraft ever-growing complexity. Emergent behaviors during the development phase causing project schedule oscillations and delays in the adequate time to market, associated with accident statistics after entering into service phase (especially those associated with Loss of Control in Flight), force new approaches for the development of new aircraft. Based on this scenario, this manuscript describe the efforts to develop a flight simulation-engineering center based on a robotic motion platform. This promising configuration might contribute to overcome some of the previous problems due to augmented motion platform workspace. However, the limited robot payload capacity and the need for a commercial jet representative cockpit, generate critical design constraints and technological challenges to implement this configuration. This manuscript details the design strategy to build the flight simulator assisted by a robotic motion platform and also analyses possible applications.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper presents the SIVOR project, an anthropomorphic-robotic flight simulator under development at the Aeronautics Institute of Technology (ITA), discussing the contribution of an additional 7th degree of freedom (DOF) provided by a linear unit to improve the pilot perception inside the flight simulator. In this context, starting from a canonical washout filter (CWF) implementation, a model-based comparative evaluation – regarding the pilot sensation – is performed considering (i) models of the robotic system with and without the linear unit, (ii) modified versions of the motion-cue algorithm (MCA), (iii) and perception models of the human vestibular system. Such integrated model is used also as the first verification for a predefined flight mission. The results obtained so far suggest an improvement on the representation of the linear acceleration as a larger workspace is provided, though also highlighting the need for further developments on the MCA structure for a better usage of the near feature.

© 2019, Journal of Aerospace Technology and Management. All rights reserved.This paper presents a detailed analysis about the implementation of a washout filter on the SIVOR (Simulador de Voo Robótico – Robotic Flight Simulator) project. The main objective of this project is to develop, on an anthropomorphic robot, a flight simulator which can be used as an Engineering Development System (EDS) and a pilot training platform, capable of providing feelings the pilot would only have in more intensive maneuvers, such as losses/gains of G in aircraft flight tests. The SIVOR project also has the objective of providing a cost-efficient and flexible tool that can be used during the design phases of aircrafts. One of the demanded features of such simulator is a representative behavior of its motion system, which is achieved by an adequate implementation of the washout filter. To the best knowledge of the authors, there are no works in the literature that present a detailed discussion about the implementation of a classical washout filter in such flight simulator, especially when the translational channel is used to its limits. Experimental results to support the proposed solutions are presented herein.

© 2019 IAAThis work proposes an alternative method for solving the two-point boundary value problem concerning to Earth-Moon bi-impulsive trajectories in the dynamics of the planar bi-circular restricted four-body problem, which describes the motion of a space vehicle subjected to the gravitational attraction of Earth, Moon and Sun. Initially, the space vehicle is at a circular low Earth orbit (LEO) with prescribed altitude. After applying the first impulsive velocity increment, the space vehicle is inserted into a transfer trajectory. The second velocity increment is applied to decelerate and circularize the movement of the space vehicle at a circular low Moon orbit (LMO) with prescribed altitude. To solve this problem, a new two-point boundary value problem (TPBVP) is formulated, which includes an unknown value of the Jacobi integral at the departure time, and, a prescribed value at the arrival time. Since the Jacobi integral is not a first integral for the four-body problem, it is taken as additional state variable, and, its variational equation is added to the system of differential equation in the description of the dynamics of the space vehicle. Taking into account the boundary conditions, expressions for the velocity increments are deduced from the Jacobi integral computed at the initial and final times. Based on this new TPBVP, a numerical procedure is proposed to obtain different families of Earth-Moon trajectories with decreasingly fuel consumption.

© 2019 IEEE.The present paper proposes the application of Model Predictive Control (MPC) to the bipedal walking problem. Classically, bipedal robots maintains constant height of the center of mass (CoM) during walking, since this constraint makes the underlying dynamical system linear. Nevertheless, researches show that vertical CoM motion is one of many mechanisms humans use to reduce energetic cost during walking. In this paper, we show that if the height is modified through a predefined function, the system becomes linear time-varying, which may be handled by MPC techniques. By means of simulations, the stability behavior of the robot is verified. Finally, a high-fidelity simulation model based on the Gazebo simulator is used to validate the energetic cost reduction due to the vertical CoM motion.

© 2019 American Institute of Aeronautics and Astronautics. All rights reserved.This paper presents an aerodynamic analysis of an airship through a computational tool, aiming to obtaining aerodynamic coefficients to be used in the design of novel airship models. A comparison between the model from simulation and from the wind tunnel test is used to validate the computational method. Due to the geometry presented by airships the analytical estimation of their coefficients becomes extremely difficult. Thus, computational tools can assist in the preliminary design of this type of air vehicle, as well as providing preliminar aerodynamic parameters, reducing the number of batteries required for wind tunnel tests. The description of the aerodynamic behavior of the airship was performed using the XFLR5 software, the modeling and setup details used will be presented in the course of this paper. The results obtained were validated through the comparison analysis presented between simulations and previous experimental results obtained in a wind tunnel using the YEZ-2A airship.

© 2019 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.This paper presents a methodology employed to characterize the aeroelastic behavior of an Unmanned Aerial Vehicle (UAV) with high aspect ratio and structural flexibility. Commonly, modal characteristics of aircraft are experimentally obtained by means of a Ground Vibration Test (GVT), which in turn could be used to correlate and update numerical models and further applied to aeroelastically characterize the aircraft. The input-Output experimental modal analysis is not easily applied to aeroelastic tests in actual flight conditions because of the difficulties measuring the actual inputs due to aerodynamic loads. Therefore, the Ouput-Only (O-O) approach also known as Operational Modal Analysis (OMA) was used to identify the modal characteristic of aircraft using accelerometers and strain sensors. In this study the OMA based on the Enhanced Frequency Domain Decomposition (EFDD) was applied to process the operational vibration data. This paper discusses and compares the results between Input-Output modal analysis and OMA approaches. A numerical flutter analysis was performed to observe the evolution of aeroelastic damping and frequencies as a function of airspeed, and to understand coupling mechanisms. The Aircraft aeroelastic behavior is studied for different flight conditions. The g-method for aeroelastic stability analysis was employed. Based on information from the GVT a flight test planning was conducted. The data acquisition system is described below.

© 2019 American Institute of Aeronautics and Astronautics. All rights reserved.This paper proposes a methodology based on multidisciplinary optimization for sizing the fins of a Lighter-Than-Air (LTA) vehicle that merges the airship and tethered aerostat functionalities. The purpose of this design is to improve the airship’s stability in a tethered flight condition by expanding fin dimensions. Therefore, an optimum sizing of the fins that meets the minimum stability requirements of both free and tethered flight conditions is approached. This study integrates in a concurrent way the mathematical modeling of the tethered airship and the methodology for fins sizing. A design vector containing initial geometric parameters of the airship with different fins size is optimized with respect to the aerodynamic stability of the tethered airship. The parameters related to the empennage is varied restricted to parameterized equations that describe the airship dynamics in free and tethered flight condition. The stop criterion of the optimization processes is obtained when the airship dynamics meets the minimum requirements used to compose the cost function based on the aerodynamic mode damping, resulting in the optimized dimension of the airship fins. This design enables to expand the airship flight envelope, ensuring a stable flight when hovering in a tethered flight condition and ensuring maneuverability to the airship for performing a free flight.

© Published under licence by IOP Publishing Ltd.This work investigates an alternative strategy to exploit future communications satellite generations including a final stage of lunar observations. For that, we explore impulsive transfers between geostationary orbits and lunar gravitational capture orbits in a full 4-body dynamical model with the Sun, Earth, Moon and spacecraft. Criteria to seek natural transfer orbits between the geostationary orbit and the vicinity of the Moon are defined considering escape properties of trajectories of the Circular Restricted Three Body Problem (CR3BP) as a guide. Namely, we select initial conditions of the 4-body model with energies that favors Earth-Moon transfers that remain around the Moon for a long time. As a case of study, we selected the current Brazilian geostationary satellite Star One C4. After a broad analysis of initial conditions and their transport behavior, we select potential transfers that reaches a near vicinity of the GEO orbit with an sufficiently small inclination with respect to the terrestrial equator. Time evolution of candidate solutions are analyzed and Δν budget and propellant mass are computed. As well as some current proposals for space debris mitigation, our strategy requires that additional mass of propellant besides onboard propulsion systems to perform final maneuvers have to be foreseen in the design of future generations of these communication satellites.

Copyright © 2019 by the International Astronautical Federation (IAF). All rights reserved.In this paper we investigate the role played by Jupiter in Earth-Mars transfers with a Venus flyby. For that, transfers are computed exploring the natural dynamics of the Restricted Three-Body Problem framework under the influence of the Sun and Jupiter gravitational potentials. The motivation for the gravity assist by Venus is two-fold. First, to design a mission to obtain data both from Venus and Mars, and second, to seek interesting solutions for a one-way or a round trip to Mars, providing a more flexible time window for a eventual return to the Earth. For the sake of comparison, direct Earth-Mars transfers are also built in the same framework. In both analysis, four parameters at departure of Earth are defined, while a fifth parameter appears in the transfers with the swing-by maneuver by Venus. We present our results and explore the effect of Jupiter in the trade-off between the Earth-Mars cost and the total Earth-Mars flight time. Additionally solutions with reduced waiting time for Hohmann transfer return to the Earth with higher values of total ?v are reported. We conclude suggesting possible applications and extensions of this preliminary analysis.

© 2018, © 2018 Taylor & Francis Group, LLC.A numerical study of the combustion of lean methane/air mixtures in a porous media burner is performed using novelty geometry, cylindrical annular space. The combustion process takes place in the porous space located between two pipes, which are filled with alumina beads of 5.6 mm diameter forming a porosity of 0.4. The outer tube diameter of 3.82 cm is isolated; meanwhile the inner tube of 2 cm in diameter is covered by a continuous set of thermoelectric elements (TE) for transforming heat energy into electricity. To achieve and maintain the proper temperature gradient on TE, convective heat losses are considered from the TE. Computer simulations focus on the two-dimensional (2D) temperature analysis and displacement dynamics of the combustion front inside the reactor, depending on the values of the filtration velocity (0.1 to 1.0 m/s), the heat loss coefficient from the internal cylinder (400–1500 W/m2/K), and the fuel equivalence ratio (0.06– 0.5). The conditions that maximized the overall performance of the process of energy conversion are: 0.7 m/s of the filtration velocity, 0.363 of the fuel equivalence ratio and 1500 W/(m2·K) of the heat transfer coefficient from the internal cylinder, to obtain 2.05 V electrical potential, 21 W of electrical power, and 5.64% of the overall process efficiency. The study shows that the cylindrical annular geometry can be used for converting the energy of combustion from lean gas mixtures into electricity, with a performance similar to the specified by manufacturers of thermoelectric elements (TE).

© 2019 Elsevier Masson SAS Flow past a sudden expansion is found in a number of engineering equipment of practical relevance. This article presents numerical results for turbulence structure and heat transfer in flow past a two-dimensional backward-facing-step channel with a porous insert using linear and non-linear eddy viscosity macroscopic models. The expansion ratio is 1:3. The non-linear turbulence models are known to perform better than classical eddy-diffusivity models due to their ability to simulate important characteristics of the flow. Parameters such as porosity, permeability and thickness of the porous insert are varied in order to analyze their effects on the flow pattern, particularly on the damping of the recirculating bubble after the porous insertion. The numerical technique employed for discretizing the governing equations is the control-volume method. The SIMPLE algorithm is used to correct the pressure field. Wall functions for velocity and temperature are used in order to bypass fine computational close to the wall. Results showed that the recirculating bubbles simulated with the linear model were shorter than those calculated with non-linear theories. Thickness of the insert had a more pronounced effect in suppressing the recirculating bubble than permeability or porosity. Results for the statistical field indicate that using porous inserts dampens generation of turbulence along the channel and concentrate conversion of mean mechanical energy into turbulence inside the porous material. Inserting a porous substrate past the expansion seems to be a practical way to decrease the sudden variations on C f and St.

© 2019 Elsevier Ltd This work presents numerical results for the thermal performance of a Solar Volumetric Receiver (SVR). The Thermal Non-Equilibrium Model and Rosseland approximation were used. Radiation boundary condition was implemented at the absorber inlet. The numerical technique employed for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was used to handle the pressure-velocity coupling. Effects of inlet velocity (u in ), porosity (ϕ), medium permeability (K), and thermal conductivity ratio (k s /k f ) on the solid and fluid temperatures were investigated. Reduction of temperatures as porosity increases or thermal conductivity decreases was observed, in addition to an increase in entry length for lower porosities or higher thermal conductivity ratios. Increase in inlet solid temperature as permeability increases was accompanied by a longer entry length and reduced final equilibrium temperature.

© 2018 Elsevier LtdKnowledge on the effects of porosity and thermal conductivity ratio on double-diffusive transport are much needed for optimum design and analysis of a number of engineering equipment. So far, the open literature seems to lack specific investigations on the effects of those two parameters on overall heat and mass transfer in cavities. This work contributes to such much-needed study on double-diffusive convection in a porous square cavity. Turbulent flow regime and aiding drive cases were considered. Governing equations were time- and volume averaged. Turbulence was handled with a macroscopic two-equation model. The thermal non-equilibrium hypotheses was employed to analyze energy transport across the enclosure. Mass transport assumes a binary mixture with solute characterized by its mass fraction. Equations were discretized with the control volume method numerically relaxed using the SIMPLE method. Here, two situations are investigated regarding the effect of porosity. First, porosity is varied along with permeability. Second, permeability is fixed while porosity takes different values. Results indicated that reducing both porosity and permeability induced flow recirculation and increased overall heat and mass transfer, leading to higher levels of turbulent kinetic energy. Such effects are less pronounced when permeability was kept constant while varying porosity. Further, increasing the thermal conductivity ratio substantially affected flow recirculation in the cavity, enhancing, ultimately, turbulence and mass transfer.

© 2019 Begell House Inc. All rights reserved.Solar energy is an abundant source of clean and renewable energy for heat and power production. In this work we present numerical results for the thermal performance of a Solar Volumetric Receiver (SVR). The Thermal Non-Equilibrium Model was employed along with radiation boundary conditions. The numerical technique used for discretizing the governing equations was the control volume method with a boundary-fitted non-orthogonal coordinate system. The SIMPLE algorithm was applied to handle the pressure-velocity coupling. Effects of inlet velocity, medium permeability and solid-to-fluid thermal conductivity ratio on temperature distributions within the absorber were investigated. Reduction of temperatures as thermal conductivity ratio decreases was observed in addition to an increase in entry length for higher thermal conductivity ratios. Increase in inlet solid temperature as permeability increases was accompanied by a longer entry length and reduced final equilibrium temperature.

© 2019 by ASME.This work presents a study of double-diffusive free convection in a porous square cavity under turbulent flow regime and with aiding drive. The thermal nonequilibrium model was employed to analyze the energy and mass transport across the enclosure. Governing equations were time- and volume-averaged according to the double-decomposition concept. Analysis of a modified Lewis number, Lem, showed that for porous media, this parameter presents opposite behavior when varying the thermal conductivity ratio or the Schmidt number, while maintaining the same value for Lem. Differently form free flow, the existence of the porous matrix contributes to the overall thermal diffusivity of the medium, whereas mass diffusivity is only effective within the fluid phase for an inert medium. Results indicated that increasing Lem through an increase in Sc reduces flow circulation inside porous cavities, reducing Nuw and increasing Shw. Results further indicate that increasing the buoyancy ratio N promotes circulation within the porous cavity, leading to an increase in turbulence levels within the boundary layers. Partial contributionsof each phase of the porous cavity (solid and fluid) to the overall average Nusselt number become independent of n for higher values of the thermal conductivity ratio, ks/ kf. Further, for high values of ks/kf, the average Nusselt number drops as N increases.

© 2019 by the authors.The surface melting of a NiTi superelastic alloy using a high-power laser Yb:Fiber was investigated. The influence of this process on the microstructural and mechanical properties was also examined. The reference material was a 3 mm nitinol strip with a homogeneous austenitic B2 phase. For the laser surface melting process, input fluences were applied from 17.5 to 45 J/mm2. The morphology of the structure and the chemical composition of several regions were determined by optical microscopy, scanning electron microscopy, dispersive energy spectra, and X-ray diffraction techniques. The mechanical properties, such as modulus of elasticity and hardness, were determined using nanoindentation and microindentation techniques. The greatest surface finishing of the fusion zone was observed for the condition 35 J/mm2. Three well-defined regions (fusion zone (FZ), heat-affected zone (HAZ), base metal (BM)) could be observed and dimensions of grain size, width, and depth of the melted pool were directly affected by the laser fluence. The geometry of the molten pool could be controlled by the optimization of the laser parameters. High laser fluence caused preferential volatilization of nickel, dynamic precipitation of intermetallic phases, including Ti2Ni, Ni3Ti, and Ni4Ti3, as well as solubilization of TiC in the matrix, which led to grain refinement. Thus, high laser fluence is a suitable technique to enhance mechanical properties such as hardness and Young’s modulus.

© 2019 Society of Plastics EngineersAn experimental investigation of mode-I translaminar fracture toughness and fatigue crack growth behavior of a carbon fiber-epoxy plain weave laminate manufactured by resin infusion under flexible tooling (RIFT) is presented in this article. Pre-cracked compact tension (CT) specimens were used to perform both quasi-static and fatigue tests. Different data reduction techniques for fracture toughness calculation were used and compared with each other. The ASTM E399 test method was modified to account for the material orthotropy and specimen geometry effects using a correction function based on a numerical evaluation of the strain energy release rate. The proposed modification shows good agreement against other experimental methods found in the literature and its application was validated for fatigue tests. Fatigue testing shows that failure in undesired modes is likely to occur prior to translaminar fracture, which was attributed to a higher tensile fatigue threshold than compression or shear fatigue threshold presented by the composite in analysis. Increasing the specimens’ initial notch length was a solution for avoiding these types of failure. The experimental results were compiled in the form of a Paris curve, and their particularities were discussed. A fractographic analysis was carried out to define damage patterns and its evolution process in both types of tests. POLYM. COMPOS., 40:3791–3804, 2019. © 2019 Society of Plastics Engineers.

© 2019 Elsevier LtdConsidering the design of aerospace structures, an experimental campaign is essential for validating the sizing methodology and margins of safety. Particularly for buckling-critical cylindrical shells, the traditional buckling test could lead the specimen to permanent damage. Therefore, the validation of nondestructive experimental procedures for estimating the buckling load of imperfection-sensitive structures from the prebuckling stage is receiving more attention from the industry. In this context, this paper proposes an experimental verification of the robustness of a vibration correlation technique developed for imperfection-sensitive structures. The study comprises three nominally identical unstiffened composite laminated cylindrical shells. Each specimen is tested 10 times for buckling at DLR and, the reproducible results — within a small range of deviation between them — corroborate the equivalence of the cylinders. For the robustness assessment of the vibration correlation technique, two different buckling test facilities are considered. Furthermore, the material properties are recalculated through composite composition rules and the influence of enhanced theoretical buckling loads on the VCT predictions is verified. The experimental campaigns corroborate that the vibration correlation technique provides appropriate estimations representing the influence of the different test facilities; moreover, enhanced theoretical buckling loads can improve the predictions for some of the test cases.

© 2018 Society of Plastics EngineersAdhesive joints are being more extensively applied in the aeronautical industry, allowing for better integration between the structural parts and overall lower weight if compared with joints made with fasteners and rivets. However, a further evaluation of these new technologies is needed, once their critical fracture toughness under different environmental conditions is still unknown and this value is essential for design and certification of aircraft manufactured with these materials. Thus, this work focuses on the mode II fracture toughness characterization of carbon fiber composite laminates joined by co-bonded (CB) and secondarily bonded (SB) techniques, using EA 9695 epoxy adhesive aged at different environmental conditions (room temperature ambient—RTA and elevated temperature wet—ETW). Dynamic mechanical analysis (DMA) was used to understand the effect of moisture absorption on the glass transition of materials and on the decreasing of Mode II fracture toughness after aging. The DMA results showed a reduction of 11% in Tg values for the GIIc values of ETW samples in comparison with specimens tested at RTA condition. Reductions about 92 and 94% in Mode II fracture toughnesses were obtained for CB and SB aged specimens, respectively when compared with the toughness values obtained for specimens tested at RTA. Further inspection of the fracture surfaces using scanning electron microscope proved that light fiber-tear fracture occurred at both RTA and ETW conditions for CB joints, while fracture was mainly light-fiber-tear at RTA condition, becoming mostly cohesive after aging for SB joints. POLYM. COMPOS., 40:3220–3232, 2019. © 2018 Society of Plastics Engineers.

© 2019 Elsevier LtdThis paper presents an analytical and numerical investigation of the relationship between the compressive load level and the natural frequency variation toward a vibration correlation technique for the buckling load calculation of imperfection-sensitive isotropic cylindrical shell structures. Firstly, a back-to-basic s study is proposed and the linear equation between the applied load and the square of the loaded natural frequency is revisited. Such review considers the Flügge-Lur'e-Byrne's linear shell theory for the free vibrations of an isotropic unstiffened cylindrical shell under uniform axial loading. The demonstrated linear equation is rearranged for expressing the square of the applied load as a quadratic function of the square of the loaded natural frequency. The suggested formulation provides the analytical support to a novel vibration correlation technique that has been empirically proposed and experimentally validated for unstiffened cylindrical shells. Aiming a numerical verification based on finite element models, two cylindrical shells are defined. At first, the critical buckling load and the fundamental natural frequency for different load levels are determined and compared to the analytical results for validation of the numerical models. The finite element models are extended considering geometric nonlinearities, more realistic boundary conditions and three magnitudes of a benchmark measured initial geometric imperfection. The numerical results are considered for analyzing the variation of the natural frequency in the surroundings of buckling and for verifying the vibration correlation technique.

© 2019 Elsevier LtdTraditional buckling experiments of imperfection-sensitive structures like cylindrical shells can cause the permanent failure of the specimen. Nevertheless, an experimental campaign is crucial for validation of the design and numerical models. There is, therefore, interest in nondestructive methods to estimate the buckling load of such structures from the prebuckling stage. The vibration correlation technique allows determining the buckling load without reaching the instability point. Recently, a novel empirical vibration correlation technique based on the effects of initial imperfections on the first vibration mode demonstrated interesting results when applied to composite and metallic unstiffened cylindrical shells. In this context, this paper explores this novel approach for determining the axial buckling load of a metallic orthotropic skin-dominated cylindrical shell under internal pressure, which represents a simplified downscaled model of a launcher propellant tank. An experimental campaign consisting of buckling tests and noncontact vibration measurements for different axial load levels is conducted considering the specimen without and with three different internal pressure levels. The experimental results validate the above-mentioned vibration correlation technique for determining the axial buckling load of pressurized cylindrical shells. Moreover, finite element models are calibrated in order to evaluate the frequency variation within a broader and dense range of the axial loading leading to an assessment of the considered maximum load level and number of load steps as related to the deviation of the estimation. The results corroborate the applicability of the vibration correlation technique as a nondestructive experimental procedure to assess the axial buckling load of imperfection-sensitive orthotropic skin-dominated cylindrical shells under internal pressure.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Static line parachuting is an important technique for deploying large amounts of troops on the battlefield. The static line ties the parachute deployment bag to the aircraft; when the paratrooper jumps, the static line tightens, removing the parachute deployment bag and releasing the canopy. One of the failure modes for static line parachuting is the towed paratrooper scenario, which consists in the paratrooper being pulled by the aircraft through its static line and consequently experiencing high force levels. It is necessary to check if the paratrooper’s physical integrity is guaranteed for the entire static line parachuting operational envelope in case of a towed paratrooper incident. A numerical analysis of the towed paratrooper scenario is elaborated to meet that end, providing the means to check how the static line material and length, the paratrooper weight and the aircraft speed affect the maximum load experienced by the paratrooper. Simulation results show that there are mass values inside the operation envelope leading to impact loads surpassing the human body injury threshold and the estimated tensile strength of type VIII webbing static lines. In conclusion, one should be cautious when raising the payload for static line paratroopers, and the force transmission from the paratrooper harness to the paratrooper body should be evaluated.

© 2019 Society of Plastics EngineersAn experimental investigation of mode-I translaminar fracture toughness and fatigue crack growth behavior of a carbon fiber-epoxy plain weave laminate manufactured by resin infusion under flexible tooling (RIFT) is presented in this article. Pre-cracked compact tension (CT) specimens were used to perform both quasi-static and fatigue tests. Different data reduction techniques for fracture toughness calculation were used and compared with each other. The ASTM E399 test method was modified to account for the material orthotropy and specimen geometry effects using a correction function based on a numerical evaluation of the strain energy release rate. The proposed modification shows good agreement against other experimental methods found in the literature and its application was validated for fatigue tests. Fatigue testing shows that failure in undesired modes is likely to occur prior to translaminar fracture, which was attributed to a higher tensile fatigue threshold than compression or shear fatigue threshold presented by the composite in analysis. Increasing the specimens’ initial notch length was a solution for avoiding these types of failure. The experimental results were compiled in the form of a Paris curve, and their particularities were discussed. A fractographic analysis was carried out to define damage patterns and its evolution process in both types of tests. POLYM. COMPOS., 40:3791–3804, 2019. © 2019 Society of Plastics Engineers.

© 2018 Society of Plastics EngineersAdhesive joints are being more extensively applied in the aeronautical industry, allowing for better integration between the structural parts and overall lower weight if compared with joints made with fasteners and rivets. However, a further evaluation of these new technologies is needed, once their critical fracture toughness under different environmental conditions is still unknown and this value is essential for design and certification of aircraft manufactured with these materials. Thus, this work focuses on the mode II fracture toughness characterization of carbon fiber composite laminates joined by co-bonded (CB) and secondarily bonded (SB) techniques, using EA 9695 epoxy adhesive aged at different environmental conditions (room temperature ambient—RTA and elevated temperature wet—ETW). Dynamic mechanical analysis (DMA) was used to understand the effect of moisture absorption on the glass transition of materials and on the decreasing of Mode II fracture toughness after aging. The DMA results showed a reduction of 11% in Tg values for the GIIc values of ETW samples in comparison with specimens tested at RTA condition. Reductions about 92 and 94% in Mode II fracture toughnesses were obtained for CB and SB aged specimens, respectively when compared with the toughness values obtained for specimens tested at RTA. Further inspection of the fracture surfaces using scanning electron microscope proved that light fiber-tear fracture occurred at both RTA and ETW conditions for CB joints, while fracture was mainly light-fiber-tear at RTA condition, becoming mostly cohesive after aging for SB joints. POLYM. COMPOS., 40:3220–3232, 2019. © 2018 Society of Plastics Engineers.

© 2018 Society of Plastics EngineersAdhesive bonding technologies for thermosetting polymer composites have been applied in several industrial sectors, such as marine, automobile, construction, and aeronautical industries due to their excellent mechanical behavior over conventional joining methods. One of the main drawbacks of this joining technology is that they are prone to delamination whilst in service. The overall composite joint structural performance depends upon several factors related to the joint manufacturing process such as surfaces preparation procedure, loading condition, adhesive type, aging effects, and inspection procedures. For this reason, there is clear need to better understand how the joint behavior is affected by these factors and the failure causes in order to improve the design and the joint performance. Within this context, this work presents a comparative fractographic analysis for two different joints types named co-bonded and secondary bonded tested under Mode I delamination at room temperature. One sample of each was observed through fractographic analysis, to identify similarities and differences between the fracture aspects, which may explain differences in toughness values and fracture behaviors. The main contribution of this article is a new failure analysis methodology focused on a better understanding on failure characteristics of adhesive joints providing a deep and critical insight into main failure mechanisms and damage sequence in composite bonded joints, which may aid analytical validation and numerical models for this type of joints developed elsewhere. Although fracture toughness (GIc) values of each joint are quite similar, some failure aspects and adhesion mechanisms differentiate these two bonding technologies. POLYM. COMPOS., 40:2973–2983, 2019. © 2018 Society of Plastics Engineers.

© 2019 Elsevier Masson SASAmong the aeroelastic phenomena most commonly affecting flexible and very flexible aircraft, those caused by gusts deserve special attention due to their potential either in degrading flying qualities and ride comfort or in increasing structural loads. It is then of interest to structural loads and flight controls engineers that solutions be developed to attenuate the effects of gusts on aircraft. Particularly, the use of piezoelectric transducers arises as one of the potential solutions in the design of gust load alleviation and structural mode suppression systems. In this paper, the gust load alleviation on a flexible smart idealized wing using only piezoelectric transducers is analyzed and experimentally tested. The numerical model includes a finite-element model of the wing, employing two-node, seven-degree-of-freedom smart beam elements, assuming small deformations and neglecting transverse shear. A quasi-steady, strip-theory-based aerodynamic model is used. Two control laws are evaluated: one based on output feedback, and the other based on feedback of observed states of a truncated system. Using a gust generator, wind-tunnel tests were performed at different flow speeds and gust frequencies to validate the computational model and to verify the performance of piezoelectric transducers. The results show a considerable attenuation of the wing root bending moment, especially using two piezoelectric actuators. Important performance improvements were overall verified with feedback of observed states when compared with static output feedback, specially to decrease the participation of the elastic modes in the gust response.

© 2018 Wiley Publishing Ltd.Composite joints exhibit different behavior in regard to delamination resistance when dealing with fatigue phenomenon. This research work focuses on an investigation to understand the failure mechanisms on the interfacial strength domain for delamination onset in cocured and cobonded joints. The analysis was based on strain energy release rate versus number of cycles plots that were obtained from fatigue tests in mode I with a stress ratio R = 0.1. The analysis encompassed from the microscopic to mesoscopic level obtained from scanning electron microscopic, and the images processed to extract the most relevant fracture patterns. The main difference between the two technologies was the stress concentration at the crack tip in which the cobonded joint presents a fabric carrier that blunts the adhesive layer, then delaying the delamination. This paper provides important information and guidelines to aid designers in the selection of the best composite joint for high-performance structural applications.

© 2018 Society of Plastics Engineers This work investigates and compares the interlaminar fracture behavior of composites manufactured by vacuum-assisted resin transfer molding subjected to three different temperatures (–54, 25, and 80°C) and mode ratios (25, 50, and 75%). The results indicate ductility enhancement with increasing temperature, which were confirmed by fractographic analyses. In tested specimens with 25% mode ratio, the G I and G II values were not greatly affected by the temperature. As the temperature and the mode ratio increases, the specimens exhibited higher G I and G II values compared with those measured at −54°C. In the tested specimens with 75% mode ratio, an unstable crack propagation was observed at −54°C due to brittle behavior of matrix, which is promoted by the decrease of the adhesion represented by cusps and broken fibers in SEM images. The cusps formation is less pronounced for specimens tested at 80°C and the fracture surface is flatter compared with those tested at −54 and 25°C. POLYM. COMPOS., 40:E1029–E1040, 2019. © 2018 Society of Plastics Engineers.

© 2018 Elsevier LtdA finite element model for predicting the nonlinear aeroelastic behavior of composite panels undergoing intralaminar and translaminar progressive damage in supersonic flow is presented. The classical plate theory in conjunction with the von Kármán nonlinear strains is used for structural modeling, and the linear piston theory is used to model the aerodynamic loads. Progressive damage is modeled by a smeared cracking formulation in which stress-based, continuum damage mechanics and fracture mechanics approaches are combined. No modal reduction is performed and an iterative form of the Newmark method is used for the numerical direct integration in time of the nonlinear equations. Simulations considering different lay-ups are conducted, in which the influence of progressive damage on the aeroelastic behavior of the panels is investigated, and damage extent and failure mechanisms are assessed. The results obtained in the analyses consist in important insights concerning the flutter-induced damage in composite panels.

© 2018 Elsevier LtdThe increasing need for automatic mesh generation has led to the development of efficient triangulation algorithms that are able to discretize any 2D or 3D domain. Modern finite element formulations based on strain smoothing techniques (SFEM) provide enhanced convergence properties, preventing yet the stiffening behavior of triangular meshes. Recent research has shown that meshless methods based on triangular mapping of the integration domain can be used to produce even better convergence properties than SFEM. The present study explores the Edge-based Smoothed Point Interpolation Method (ES-PIM) as a meshless solution to investigate linear buckling on variable angle tow (VAT) laminates. Such advanced composite structures show a heterogeneous distribution of constitutive properties and thickness, presenting additional challenges to the numerical solution. Important aspects related to the transverse shear correction herein adopted are investigated, leading to interesting conclusions regarding the possibility to use the ES-PIM for conservative estimates of the critical buckling load of VAT laminates.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The effect of addition of viscoelastic layers on the acoustic scattering quadrupoles near the trailing edge of composite plates is evaluated. For modelling of the viscoelastic material the complex modulus approach was used in combination with the frequency-temperature correspondence principle. The computation of laminate stiffness is based on Classical Lamination Theory. We employ a numerical method to compute the acoustic field scattered by finite elastic plates. Based on a Boundary Element Method, this procedure solves the Helmholtz equation subject to boundary conditions related to the vibration of the plate. These conditions are recast in terms of the vibration modes of a rectangular plate. Results show that by adding viscoelastic plies to a composite plate we modify the far-field sound scattered by turbulence near an edge of the plate. Parametric studies show that this approach reduces scattered noise at resonance frequencies. Discussions on the operating temperature, positioning and thickness of the viscoelastic layers are provided.

© Universal Technology Corporation, 2018.This work presents the development of a finite element beam model accounting for structural and aerodynamic nonlinearities regarding large deflections. The total Lagrangian formulation is employed for describing the exact Timoshenko’s bending kinematics, whereas the torsion is modeled as an uniform torsion and uncoupled from the bending motion. The aerodynamic description is based on an unsteady 2D strip theory in the time domain with the Jones approximation for Wagner’s function. In addition, a follower forces assumption combined with a simplified stall model are assumed, in which the lift-curve slope is interpolated based on the experimental data available in the literature. Very good correlation between experimental and predicted aeroelastic responses has been obtained for a highly elongated plate-like wing structure with a ballast at the free end.

© 2019 The Author(s) Published by the Royal Society. All rights reserved.We investigate the effects of structural damping on the interaction of a turbulent eddy with flexible plates with respect to the efficiency of aerodynamic noise generation. Potential benefits are studied using a model based on a point-reacting compliant semiinfinite plate on a spring-damper foundation. This scattering problem is solved using the Wiener- Hopf technique. We compare results for semi-infinite compliant plates with finite ones. In both cases, plate vibration lead to reductions of sound radiation, especially at resonance; damping tends to reduce such acoustic benefits. We also present a formulation that considers the effect of structural damping on the acoustic properties of finite elastic plates. Numerical results are obtained by applying a boundary element method to solve the Helmholtz equation subject to the boundary conditions imposed by the plate vibration. Under specific conditions, such as high fluid loading factor and low bending-wave Mach number, the acoustic power scattered by an edge tends to be smaller than that which propagates over the plate as bending waves. Results show that structural damping attenuates these waves and may modify the far-field acoustic pressure, mostly by reducing the scattered sound at structural resonances. All models show that large damping coefficients lead to locally overdamped responses. There is thus an ideal range of structural damping to reduce both plate vibration and acoustic scattering.

Copyright © 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.The strut-braced wing aircraft configuration promises to reduce fuel burn by enabling higher spans that reduce lift-induced drag. A successful design for this configuration depends on a careful trade-off between the various sources of drag and structural weight. When using computational fluid dynamic tools for aerodynamic shape optimization, generating high-quality structured meshes for the strut-braced wing configuration becomes challenging, especially near junctions. Furthermore, mesh deformation procedures frequently generate negative volume cells when applied to these structured meshes during optimization. This paper addresses this issue by using overset meshes and a component-based parametrization technique to achieve a flexible design optimization cycle capable of handling changing junctions. This study uses this approach to minimize drag of the PADRI 2017 strut-braced wing benchmark for a fixed lift constraint at transonic flight conditions. The drag of the optimized configuration is 15% lower than the baseline due to the reduction of shocks and separation in the wing-strut junction region. This result represents an example in which high-fidelity modeling is required to quantify the benefits of a new aircraft configuration and address potential issues during the conceptual design.

© 2019 AIAA.This paper presents a conceptual study of a regional aircraft with a turboelectric propulsion system and boundary layer ingestion. The concept was designed by the installation of an additional electric propulsor at the aircraft tail cone, which is driven by generators installed on both underwing engines, aiming to ingest the fuselage boundary layer and improve the aircraft overall performance. The proposed configuration can be considered an aircraft reengining, targeting minimal changes on the reference aircraft platform, the Embraer 175-E1. Parametric variations of the thrust split ratio as well as the electric fan pressure ratio were done in order to create a design space of possible solutions for the proposed concept and also to provide insights of the aircraft key variables trends. From that, an optimized configuration not only in terms of efficiency but also regarding the concept feasibility was chosen and compared to the reference aircraft. It was determined that the studied propulsion system has a potential to provide specific air range benefits in the order of 4% to 7%.

© The Author(s) 2018.In the present work, a numerical and experimental study of the thermoacoustic instabilities of a combustor is performed. The numerical model is represented by the one-dimensional linearised Euler Equation and an n-τ formulation for flame transfer function that describes the unsteady combustion response to these acoustic disturbances. This approach is similar to other simplified models present in the literature. However, most theoretical works assume a constant density and speed of sound in the medium, which is not realistic for combustion chambers, as the mean temperature is expected to decrease spatially as one moves away from the combustion area. Hence, to compare with experiments where chamber temperature is spatially varying, we developed a numerical solution procedure, seeking eigenvalues (complex-valued frequencies ω) indicating the stability characteristics of a given mode. Due to the non-linear dependence of the flame transfer function with ω, eigenvalues are found with a non-linear root-finding method. The acquired results met those obtained experimentally, indicating that the proposed model is capable of predicting the thermoacoustic behaviour of the combustion chamber.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering.The aim of this paper is to define a methodology to minimize the adjustment effort required to comply with aircraft design performance requirements, when commercial off-the-shelf turbofan engines are installed, which is a challenge to aircraft manufactures. In order to achieve an efficient operation, a reasonable proposal is to adapt the propulsive performance by turbofan engine optimization. This work is carried out according to the following steps: (i) creation of estimated performance curves for a gas turbine from limited data; (ii) analysis of the impacts on performance and propulsive integration, applying computer simulation of the most promising engine components configuration; and (iii) matching between the lowest specific fuel consumption and the net thrust required for the cruise flight phase of the aircraft. The technical feasibility and the possible predisposition of engine manufactures to perform the implementation were also considered as critical points in this procedure. As a final result, an evaluation that presents the most suitable turbofan engine component modifications proposal to comply with engine/aircraft performance integration to be applied in the conceptual design phase was obtained.

© 2019 by American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper presents a conceptual study of a regional aircraft with a turboelectric propulsion system and boundary layer ingestion. The concept was designed by the installation of an additional electric propulsor at the aircraft tail cone, which is driven by generators installed on both underwing engines, aiming to ingest the fuselage boundary layer and improve the aircraft overall performance. The proposed configuration can be considered an aircraft reengining, targeting minimal changes on the reference aircraft platform, the Embraer 175-E1. Parametric variations of the thrust split ratio as well as the electric fan pressure ratio were done in order to create a design space of possible solutions for the proposed concept and also to provide insights of the aircraft key variables trends. From that, an optimized configuration not only in terms of efficiency but also regarding the concept feasibility was chosen and compared to the reference aircraft. It was determined that the studied propulsion system has a potential to provide specific air range benefits in the order of 4% to 7%.

© 2019 SAE International and © 2019 SAE Naples Section. All Rights Reserved.Despite syngas is a promising alternative fuel for internal combustion engines (ICEs), its extensive adoption has not been adequately investigated so far. The dedicated literature offers several fundamental studies dealing with H2/CO blends burning at high pressure and room temperature, as well as preheated mixture at low pressure. However, these thermodynamic states are far from the operational conditions typical of ICEs. Therefore, it is essential to investigate the syngas combustion process at engine-like conditions to shed light on this fuel performance, in order to fully benefit from syngas characteristics in ICE application. One of the key properties to characterize a combustion process is laminar flame speed, which is also used by the most widespread turbulent combustion models. In the first part, a database of premixed laminar burning rates at engine-like conditions for different syngas (H2/CO) blends is created based on one-dimensional unstretched flame simulations using two validated chemical mechanisms. Then the resulting laminar flame speed values are fitted using a validated in-house method based on logarithmic correlations. In the second part of the paper, these are implemented in the G-equation combustion model and three-dimensional simulations of a four stroke Spark Ignition (SI) optical access engine fueled by syngas are carried out. The combustion characteristics of two H2/CO blends (50/50 and 75/25 volume fraction, respectively) are investigated and the simulation results are compared to the available experimental data for the same fuels. This joint numerical/experimental study allows to investigate and optimize the syngas combustion for ICEs and it provides general guidelines to further understand the feasibility of this alternative fuel in terms of ICE utilizations.

Copyright © 2019 by the American Institute of Aeronautics and Astronautics, Inc.Research has shown that oxidizer swirl injection and liquefiable fuels, such as paraffin wax, can increase regression rates in hybrid rockets. However, there are few studies published on motors that use both these strategies simultaneously. This paper presents an exhaustive experimental investigation on the performance of a lab-scale hybrid rocket motor using paraffin wax and gaseous oxygen under a number of different conditions, including five different oxidizer injectors with varying levels of swirl. Prechamber length, fuel grain length, burn duration, oxidizer mass flow rate, and fuel grain geometry were modified from a baseline, and the influence on fuel regression and thrust oscillations was evaluated. Swirl injection increased regression rates up to 2.4 times that of the baseline axial injection configuration, while providing smoother operating conditions. The results show that thrust density of a hybrid rocket can be increased simultaneously by the use of a liquefying fuel and swirl injection. The results obtained also provide a unique experimental observation of the influence of several motor parameters on its performance, revealing that prechamber length and the angle of an entry slope on the grain do not contribute significantly to the performance or stability of the motor with swirl injection.

© 2019 by the authors.To mitigate the increasing concentration of carbon dioxide in the atmosphere, energy production processes must change from fossil to renewable resources. Bioenergy utilization from agricultural residues can be a step towards achieving this goal. Syngas (fuel obtained from biomass gasification) has been proved to have the potential of replacing fossil fuels in stationary internal combustion engines (ICEs). The processes associated with switching from traditional fuels to alternatives have always led to intense research efforts in order to have a broad understanding of the behavior of the engine in all operating conditions. In particular, attention needs to be focused on fuels containing relatively high concentrations of hydrogen, due to its faster propagation speed with respect to traditional fossil energy sources. Therefore, a combustion study was performed in a research optical SI engine, for a comparison between a well-established fuel such as methane (the main component of natural gas) and syngas. The main goal of this work is to study the effect of inert gases in the fuel mixture and that of air dilution during lean fuelling. Thus, two pure syngas blends (mixtures of CO and H2) and their respective diluted mixtures (CO and H2 with 50vol% of inert gases, CO2 and N2) were tested in several air-fuel ratios (stoichiometric to lean burn conditions). Initially, the combustion process was studied in detail by traditional thermodynamic analysis and then optical diagnostics were applied thanks to the optical access through the piston crown. Specifically, images were taken in the UV-visible spectrum of the entire cycle to follow the propagation of the flame front. The results show that hydrogen promotes flame propagation and reduces its distortion, as well as resulting in flames evolving closer to the spark plug. All syngas blends show a stable combustion process, even in conditions of high air and fuel dilution. In the leanest case, real syngas mixtures present a decrease in terms of performance due to significant reduction in volumetric efficiency. However, this condition strongly decreases pollutant emissions, with nitrogen oxide (NOx) concentrations almost negligible.

© 2019, Emerald Publishing Limited.Purpose: This paper aims to present experimental and numerical analyses of fused filament fabrication (FFF) printed parts and show how mechanical characteristics of printed ABS-MG94 (acrylonitrile butadiene styrene) are influenced by the void volume fraction, cooling rate and residual thermal stresses. Design/methodology/approach: Printed specimens were experimentally tested to evaluate the mechanical properties for different printing speeds, and micrographs were taken. A thermo-mechanical finite element model, able to simulate the FFF process, was developed to calculate the temperature fields in time, cooling rate and residual thermal stresses. Finally, the experimental mechanical properties and the microstructure distribution could be explained by the temperature fields in time, cooling rate and residual thermal stresses. Findings: Micrographs revealed the increase of void volume fraction with the printing speed. The variations on voids were associated to the temperature fields in time: when the temperatures remained high for longer periods, less voids were generated. The Young's Modulus of the deposited filament varied according to the cooling rate: it decreased when the cooling rate increased. The influence of the residual thermal stresses and void volume fraction on the printed parts failure was also investigated: in the worst scenarios evaluated, the void volume fraction reduced the strength in 9 per cent, while the residual thermal stresses reduced it in 3.8 per cent. Originality/value: This work explains how the temperature fields can affect the void volume fraction, Young's Modulus and failure of printed parts. Experimental and numerical results are shown. The presented research can be used to choose printing parameters to achieve desired mechanical properties of FFF printed parts.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering. The present work investigates the mechanical properties of continuous carbon fiber-reinforced thermoplastic by testing composite specimens which were manufactured using an innovative process based on the fused filament fabrication (FFF, analogous to FDM ® ). The adopted testing procedures and their results are presented, as well as an introduction to the manufacturing process, which is patented by Markforged Inc. The experimental mechanical properties (stiffness and strength) of the composite specimens, measured in tensile (longitudinal and transverse), compression (longitudinal) and in-plane shear are reported. The asymptotic homogenization technique is applied in order to predict the elastic mechanical properties of the carbon fiber-reinforced lamina. In contrast to recent studies, this investigation has revealed that considering Nylon as the thermoplastic matrix embedding the continuous fiber consistently underpredicts the transverse and in-plane shear elastic properties of the reinforced laminae. These results suggest that the composition of the thermoplastic resin is not exactly the same for the unreinforced and reinforced filaments. Additionally, cross-sectional micrographs of specimens are analyzed in detail and considerable insight has been gained concerning the thermoplastic resin of reinforced filaments.

© 2019 Sociedade Brasileira de Quimica. All rights reserved.The present work presents combustion simulations of hydroxyl-terminated liquid polybutadiene loaded with ammonium perchlorate and aluminum, using Chemkin software and the “Plug Flow” type reactor. These materials are widely used in solid composite propellant formulations. Through this study, the effect of parameters of axial velocity, equivalence ratio, pressure and temperature during the firing of the propellant were discussed. The objective of this work was to discuss how to define the best parameter value based on the obtained results, and thus generate optimized formulations.

© 2019 Sociedade Brasileira de Quimica. All rights reserved.This work aims to determine the kinetic parameters of the thermal decomposition of a lubricating grease based on perfluoropolyether (PFPE) and the computational simulation of this decomposition. The determination of kinetic parameters of thermal decomposition was done by thermal analysis using thermogravimetry (TG) at different heating rates (β) of 10, 15 and 20 °C min-1. With the TG curves obtained, the kinetic parameters were determined by the kinetics methods of Goldfarb et al. and Duvvuri et al., Flynn-Wall-Ozawa and Kissinger. The activation energy of the thermal decomposition of the PFPE grease in the kinect models ranged from 63.54 to 112.3 kJ mol-1. The results of the thermogravimetry indicated that the PFPE grease is thermally stable up to 300 °C. A simulation of the thermal decomposition of the PFPE oil base was carried out by molecular dynamics simulation, using LAMMPS (Large-scale Atomic/Molecular Massively Parallel Simulator) in a temperature range of 0 to 3500 K during 50 ps. The value of the activation energy in the simulation was 92 kJ mol-1. The results show that PFPE oil base and PFPE lubricant grease can be used in high-temperature applications.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering. This paper presents a study about injectors, where the radial injector was evaluated. This type of injector was chosen because only a small amount of information on it was found. Thus, the radial injector will be compared with other two types of injectors, the orifice plate and the swirl, in terms of parameters, such as discharge coefficient (C d ), regression rate r, and specific impulse (I sp ). In respect of the regression rate, the values appeared increasingly with the test pressure and, consequently, with the injection pressure. Thus, each injector model responded in the same way as for the regression rate behavior; however, the same behavior was not observed in relation to the specific impulse.

© 2019, The Brazilian Society of Mechanical Sciences and Engineering.The interest in applying piezoelectric materials for modal analysis has been growing in the past few decades. In piezoelectric materials, both electrical and mechanical domains are coupled, i.e., these materials are able to convert electrical energy into mechanical energy and vice versa. Due to this key characteristic, they can be used in several applications as actuators or sensors. Furthermore, some piezoelectric materials exhibit a predominant coupling, which makes them more efficient when used for specific purposes/applications. This is the case of the polyvinylidene fluoride (PVDF) which is widely used as a sensor. An advantage associated with the PVDF is its small influence on the results, due to the low thickness and high flexibility; sometimes, its influence is completely neglected. The aim of this work is to evaluate the influence of a single PVDF film on a flexible beam model. For this purpose, an efficient methodology to verify and identify the intrusiveness level of the instrumentation is proposed, which consists in changing the sensor position (PVDF) and simultaneously acquiring the data by using a non-intrusive technique (laser vibrometer). The modal parameters (natural frequencies and damping factors) obtained by PVDF and laser vibrometer responses should be very close for each PVDF position. If this condition is satisfied, the variation of the modal parameters due to PVDF position will show the intrusiveness level imposed by the PVDF instrumentation. This research emphasizes the importance of verifying the influence of the instrumentation, even if it seems to cause merely a small intrusiveness on the dynamic system.

© 2019 Elsevier Masson SASAmong the aeroelastic phenomena most commonly affecting flexible and very flexible aircraft, those caused by gusts deserve special attention due to their potential either in degrading flying qualities and ride comfort or in increasing structural loads. It is then of interest to structural loads and flight controls engineers that solutions be developed to attenuate the effects of gusts on aircraft. Particularly, the use of piezoelectric transducers arises as one of the potential solutions in the design of gust load alleviation and structural mode suppression systems. In this paper, the gust load alleviation on a flexible smart idealized wing using only piezoelectric transducers is analyzed and experimentally tested. The numerical model includes a finite-element model of the wing, employing two-node, seven-degree-of-freedom smart beam elements, assuming small deformations and neglecting transverse shear. A quasi-steady, strip-theory-based aerodynamic model is used. Two control laws are evaluated: one based on output feedback, and the other based on feedback of observed states of a truncated system. Using a gust generator, wind-tunnel tests were performed at different flow speeds and gust frequencies to validate the computational model and to verify the performance of piezoelectric transducers. The results show a considerable attenuation of the wing root bending moment, especially using two piezoelectric actuators. Important performance improvements were overall verified with feedback of observed states when compared with static output feedback, specially to decrease the participation of the elastic modes in the gust response.

© Statement The authors confirm that they, and/or their company or organization, hold copyright on all of the original material included in this paper.The workload assessment to perform a full autorotation on the AS-350 aircraft (Airbus Helicopters) was performed during a Flight Test Campaign with 80 flight hours and 227 data collection procedures, considering 10 pilots with different piloting skill levels, among such military pilots, flight instructors, and test pilots. During the tests, these pilots were subjected to unexpected engine failures, to evaluate the actual reaction time of each pilot, and to test the ability to make a safe landing under the conditions prescribed by the aircraft manufacturer. The testing method used began with unexpected engine failures when only the lead test pilot knew that the engine failure would be simulated. In the sequence, several points of autorotation were performed, from the simplest profile to the most complex. All the procedures have registered the performance parameters and handling qualities of the aircraft, along with the physiological parameters of the pilots. The aircraft was equipped with dedicated instrumentation for in-flight testing and the pilots have been instrumented with an Electroencephalogram (EEG), Electrocardiogram (EKG), Respiration Belt and Galvanic Skin Response (GSR), Eye Tracking and Face Recognition Camera equipment. This instrumentation was employed to determine physiological markers that could determine the pilot workload, quantitatively, reducing the subjectivity of measures that use only qualitative scales of evaluation, such as Handling Qualities Rate (HQR) and Bedford Workload Scale (WL). In this work, only the preliminary results of the analysis obtained by the Galvanic Skin Response markers will be presented. Major potential applications of the results from the present research range from cockpit design guidelines and human-machine interface systems for supporting pilotage such as more effective alarm systems, interactive cockpits, enhancement of active autopilots with semi-automatic flight commands. Besides that, the results and conclusions from this research can also improve processes and methods for the training-based formation of pilots, along with the development of flight simulators with physiological measurements parameters quantification, feeding back data for a piloting performance assessment.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Aggressive targets for reducing aviation environmental impacts require considerable improvements in aircraft design such as nonconventional aerodynamic configurations, new materials and more efficient systems. This scenario poses airframe manufacturers to make more efficient products only achievable by making a complete integrated design between airframe and systems. In this sense, the aircraft design shall be committed to the maximum efficiency and minimum waste of useful energy (exergy destruction). The concept of exergy analysis has already been successfully applied to evaluate, compare and optimize thermal systems and chemical processes in other industrial fields. Thereby, this paper presents how exergy analysis can be used as a tool for aircraft design and shows an application of the method to evaluate competitive propulsion system architectures for a regional aircraft.

© Universal Technology Corporation, 2018.The design of the conventional configuration of commercial aircraft, composed by a tube fuselage, a cantilever wing and an empennage, has been improved since its introduction in the 1950s and it is unlikely that great improvements should occur without drastic changes. The strut braced wing aircraft presents itself as an option. The main difference lies on a strut connecting the wing to the fuselage, reducing the bending moment of the wing and, consequently, its weight. Alternatively, the wing span could be increased, or even the wing thickness decreased, without great weight penalties. This combination of geometric changes reduces drag and improves performance. To evaluate possible aeroelastic issues that might hinder the development of this configuration, a parametric flutter analysis is performed based on aircraft of regional aviation size. As a result it was observed that: (a) increasing the wing aspect ratio from 8.3 to 12 decreases the flutter speed in 20%; (b) if the engine is positioned exactly at the wing and strut intersection at 70% of the wing span instead of 50%, an increase of 30% in flutter speed is obtained; (c) and that the flutter speed can be increased by 35% if the spanwise wing and strut intersection is moved from 70% to 30 % of the span.

© Universal Technology Corporation, 2018.Nonlinear aeroelastic phenomena are continuously investigated in aeronautical researches. The nonlinearity nature can be aerodynamic or structural. This work will investigate aeroelastic nonlinearities in a very flexible wing. A flutter analysis is proceeded in order to evaluate the error between the computational results and the experiment. Since the linear flutter theory considers small disturbances, nonlinear phenomena are expected. Both wind tunnel and computational experiments time series shall be analyzed and the evaluation if the system presents chaotic behavior will be performed through the 0-1 test.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper identifies, characterizes and describes correction procedures for uncertainty sources associated with fast-response pressure sensitive paint (PSP) optical and image acquisition systems, including fixed pattern noise, non-linear CMOS sensor response and optical vignetting. Data on a typical CMOS camera was acquired using an easy to manufacture integrating sphere, and image correction procedures were developed having a typical wind tunnel environment in mind. For validation, corrections were applied to data on pressure distribution over a NACA 0012 airfoil in transonic flow. A significant improvement in data accuracy was observed.

© 2019 by German Aerospace Center (DLR). Published by the American Institute of Aeronautics and Astronautics, Inc.Aircraft equipped with an electric propulsion system are of increasing interest to the aeronautical community. This work focuses on the optimal performance of such aircraft during the climb phase, since it can be very energy consuming and demanding to the propulsion system. Analytical expressions for the optimal lift coefficient, throttle and velocity are derived as solutions to optimal control problems, for steady climb and for a simplified, linear accelerated climb, without a specified final time. The total energy cost and altitude gain are also derived in parametric form, allowing quick, useful estimations for conceptual design and performance analysis. This is supplemented by simulations in order to provide a quantitative insight to the problem.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.Flow and noise predictions of the tandem cylinder benchmark are performed using the open-source computational fluid dynamics code (CFD) Stanford University Unstructured (SU2). The numerical results were obtained using the Delayed Detached Eddy Simulation (DDES) approach with the new shear-layer adapted sub-grid length scale (SGS) for faster transition between RANS and LES. The Ffowcs Williams–Hawkings (FWH) analogy is used to propagate the pressure fluctuations to the farfield. Both flow and noise results are compared with experimental measurements from the Basic Aerodynamic Research Tunnel (BART) and Quiet Flow Facility (QFF) at NASA Langley Research Center. The compressible simulations are carried out on the mandatory 2-D grid from the ATAAC project with a spanwise extension of 3.0D, two different spanwise discretization were used to analyze the discretization effect. The comparison shows that the shear-layer adapted (∆SL A) is less grid dependent and more accurate than the standard (∆max) SGS.

© 2018 Elsevier B.V.High-order spectral element methods (SEM) for large-eddy simulation (LES) are still very limited in industry. One of the main reasons behind this is the lack of robustness of SEM for under-resolved simulations, which can lead to the failure of the computation or to inaccurate results, aspects that are critical in an industrial setting. To help address this issue, we introduce a non-modal analysis technique that characterizes the numerical diffusion properties of spectral element methods for linear convection–diffusion problems, including the scales affected by numerical diffusion and the relationship between the amount of numerical diffusion and the level of under-resolution in the simulation. This framework differs from traditional eigenanalysis techniques in that all eigenmodes are taken into account with no need to differentiate them as physical or unphysical. While strictly speaking only valid for linear problems, the non-modal analysis is devised so that it can give critical insights for under-resolved nonlinear problems. For example, why do SEM sometimes suffer from numerical stability issues in LES? And, why do they at other times be robust and successfully predict under-resolved turbulent flows even without a subgrid-scale model? The answer to these questions in turn provides crucial guidelines to construct more robust and accurate schemes for LES. For illustration purposes, the non-modal analysis is applied to the hybridized discontinuous Galerkin methods as representatives of SEM. The effects of the polynomial order, the upwinding parameter and the Péclet number on the so-called short-term diffusion of the scheme are investigated. From a non-modal analysis point of view, and for the particular case of hybridized discontinuous Galerkin methods, polynomial orders between 2 and 4 with standard upwinding are found to be well suited for under-resolved turbulence simulations. For lower polynomial orders, diffusion is introduced in scales that are much larger than the grid resolution. For higher polynomial orders, as well as for strong under/over-upwinding, robustness issues can be expected due to low and non-monotonic numerical diffusion. The non-modal analysis results are tested against under-resolved turbulence simulations of the Burgers, Euler and Navier–Stokes equations. While devised in the linear setting, non-modal analysis successfully predicts the behavior of the scheme in the nonlinear problems considered. Although the focus of this paper is on LES, the non-modal analysis can be applied to other simulation fields characterized by under-resolved scales.

© Springer Nature Switzerland AG 2019.We consider the suitability of implicit large-eddy simulation (iLES) approaches via discontinuous Galerkin (DG) schemes. These are model-free eddy-resolving approaches which solve the governing equations in unfiltered form and rely on numerical stabilization techniques to account for the missing scales. In DG, upwind dissipation from the Riemann solver provides the baseline mechanism for regularization. DG-based iLES approaches are currently under rapid dissemination due to their success in predicting complex transitional and turbulent flows at moderate Reynolds numbers (Uranga et al, Int J Numer Meth Eng 87(1–5):232–261, 2011, [1], Gassner and Beck, Theor Comput Fluid Dyn 27(3–4):221–237, 2013, [2], Beck et al, Int J Numer Methods Fluids 76(8):522–548, 2014, [3], Wiart et al Int J Numer Methods Fluids 78:335–354, 2015, [4]). However, at higher Reynolds number, accuracy and stability issues can arise due the highly under-resolved character of the computations and the suppression of stabilizing viscous effects.

© 2019 Elsevier B.V.The authors regret that Fig. 4 is the same as Fig. 5 in the original publication, and that the correct Fig. 4 is missing. Please see below for the correct Fig. 4: [Figure presented] The authors would like to apologise for any inconvenience caused.

© 2019 Elsevier B.V.The limitations of the usual techniques applied for gear grinding burn detection are extended by the increasing demands on quality control within industrial feasibility. Although widely used, nital etching technique has a subjective character. Alternative techniques such as magnetic Barkhausen noise and X-ray diffractometry also present drawbacks such as variability of output based on external energy input that depends on parameter settings, high cost and destruction of tests parts. Due to this technical gap, an alternative method is suggested, where the remanent induction of a workpiece is measured by means of a Hall probe. The objective of this concept is to reduce external inputs on the workpiece, measuring its natural signal and correlating it to the material property induced by the damage. In this study, three different degrees of damage were investigated with the Hall method, covering damages with phase transformation as well as with modifications on the residual stress state. According to the results obtained, an alteration in the remanent induction which is directly correlated to the burn degree, was detected. The micro-magnetic theory establishes a correlation between the remanent magnetic induction and material hardness as well as residual stress state. The signal alteration detected by the Hall method is in accordance with the micro-magnetic theory for all three degrees of burn analyzed.

© 2018 Elsevier B.V.TWIP steel weld spots were produced by varying the following welding parameters: welding current, welding time and electrode clamping force. Hardness distributions along the weld spots cross section were obtained by Vickers microindentations. The mechanical strength and failure modes of the weld spots were assessed by tensile-shear tests. Weibull statistics was applied to statistically analyse the data from tensile-shear loading. The results highlighted the influence of welding parameters variations on the Vickers hardness and residual stress state. These properties have a positive correlation to the failure modes and so the mechanical reliability of the weld spots. Welds that failed in pullout mode and partial-interfacial failure mode have statistically higher load bearing capacity than those in interfacial failure mode. The combination of a welding current of 8 kA with a welding time of 16 cycles and an electrode clamping force of 2 kN showed to be the optimum parameters for the investigated TWIP steel weld spots. By using this optimum setup, it was possible to supress interfacial failure mode and to obtain pullout as the predominant failure mode, considerably increasing the mechanical reliability of the weld spots.

© 2019 IAAThis work proposes an alternative method for solving the two-point boundary value problem concerning to Earth-Moon bi-impulsive trajectories in the dynamics of the planar bi-circular restricted four-body problem, which describes the motion of a space vehicle subjected to the gravitational attraction of Earth, Moon and Sun. Initially, the space vehicle is at a circular low Earth orbit (LEO) with prescribed altitude. After applying the first impulsive velocity increment, the space vehicle is inserted into a transfer trajectory. The second velocity increment is applied to decelerate and circularize the movement of the space vehicle at a circular low Moon orbit (LMO) with prescribed altitude. To solve this problem, a new two-point boundary value problem (TPBVP) is formulated, which includes an unknown value of the Jacobi integral at the departure time, and, a prescribed value at the arrival time. Since the Jacobi integral is not a first integral for the four-body problem, it is taken as additional state variable, and, its variational equation is added to the system of differential equation in the description of the dynamics of the space vehicle. Taking into account the boundary conditions, expressions for the velocity increments are deduced from the Jacobi integral computed at the initial and final times. Based on this new TPBVP, a numerical procedure is proposed to obtain different families of Earth-Moon trajectories with decreasingly fuel consumption.

© 2018 Elsevier LtdIn this work, viscoelastic materials are adopted for handling aeroelastic features of typical section models with three degrees-of-freedom, which present non-smooth, free-play type nonlinearities in their control surface. A rotational viscoelastic damper is added to the resilient element associated to the control surface motion of the typical section. Equations of motion are derived accounting for the viscoelastic damper dependence on frequency and temperature. For this, a fractional derivatives-based viscoelasticity constitutive law is considered. Aerodynamic forces are introduced based on linear potential unsteady aerodynamics accounting for arbitrary airfoil motions. The aeroelastic behavior is investigated through time domain simulations, from which bifurcation diagrams are constructed. Numerical results show that the addition of viscoelastic damping can increase the flutter speed noticeably and reduce the amplitudes of limit cycle oscillations for the system under consideration. Another observed benefit provided by the viscoelastic damper is that undesirable subcritical behavior for the bifurcation onset can be eliminated or modified to have a supercritical character. The influence of temperature on the aeroviscoelastic behavior is also investigated. Using the proposed strategy, nonlinear instabilities can be controlled, improving the safety margins of aeroelastic systems.

© 2019, Springer Nature Switzerland AG.The present paper is devoted to the modeling of systems comprising a flexible rotor mounted onto an elastic base, undergoing arbitrary rotations. By using a Lagrangian approach, the equations of motion are derived for the coupled rotor-base system, considering finite element discretization for both the base and the rotor. Numerical simulations are performed for a specific configuration of the rotor-bearing system and attitude motion. Results are interpreted to evaluate, both qualitatively and quantitatively, the influence of the base motion and flexibility on the dynamic behavior of the rotor, in terms of unbalance responses. Based on the results, conclusions are drawn, especially in terms of the conditions under which the flexibility of the base is indispensable for accurate prediction of the rotor behavior.

© 2019 IOP Publishing Ltd. All rights reserved.The hydrodynamic stability of a vortex system behind two in-line wind turbines operating at low tip-speed ratios is investigated using the actuator-line method in conjunction with the spectral-element flow solver Nek5000. To this end, a simplified setup with two identical wind turbine geometries rotating at the same tip-speed ratio is simulated and compared with a single turbine wake. Using the rotating frame of reference, a steady solution is obtained, which serves as a base state to study the growth mechanisms of induced perturbations to the system. It is shown that, already in the steady state, the tip vortices of the two turbines interact with each other, exhibiting the so-called overtaking phenomenon. Hereby, the tip vortices of the upstream turbine overtake those of the downstream turbine repeatedly. By applying targeted harmonic excitations at the upstream turbine's blade tips a variety of modes are excited and grow with downstream distance. Dynamic mode decomposition of this perturbed flow field showed that the unstable out-of-phase mode is dominant, both with and without the presence of the second turbine. The perturbations of the upstream turbine's helical vortex system led to the destabilization of the tip vortices shed by the downstream turbine. Two distinct mechanisms were observed: for certain frequencies the downstream turbine's vortices oscillate in phase with the vortex system of the upstream turbine while for other frequencies a clear out-of-phase behaviour is observed. Further, short-wave instabilities were shown to grow in the numerical simulations, similar to existing experimental studies [1].

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This work aims at presenting an integrated development system to a motion real-time flight simulator using a robotic device. This flight simulator is called SIVOR (Simulador de Voo Robótico – Robotic Flight Simulator). This is a multidisciplinary project since it involves different systems with different level of complexity, which by itself give some challenges in how to develop this type of flight simulator. In order to have a flight simulator with base motion upon robotic device it is necessary the domain of systems like robotic, pilot modeling, filtering design, here called by washout filter, aeronautic modeling which includes traditional systems as automatic flight control, aerodynamic, propulsion, ground handling, sensors and actuation. Therefore a considerable effort in the development is demanded to have a representative aircraft model been executed in a real-time flight simulator with robotic motion. Thus this paper presents an integrated modeling process to represents all of the system in order to give a more maturity development cycle, in order to reduce the uncertainties presented in the begin of any project and that becomes more challenging for any complex system. The real-time motion flight simulator based upon robotic environment has a nonlinear flight mechanic model of EMBRAER 190-E2, and here won’t be presented in order to protect the intellectual property and compliance policies of EMBRAER S.A., the other systems will be explained in detail and a sensitive analysis is presented in order to demonstrated that an model based approach shall be used in this kind of flight simulator in order to speed up the maturity level of the system.

� 2019 by German Aerospace Center (DLR). Published by the American Institute of Aeronautics and Astronautics, Inc.The need for an optimized aircraft development cycle imposed by market constraints, associated with airliners demands for more cost-effective and safe operations, has become a challenge for aircraft OEM in face of new aircraft ever-growing complexity. Emergent behaviors during the development phase causing project schedule oscillations and delays in the adequate time to market, associated with accident statistics after entering into service phase (especially those associated with Loss of Control in Flight), force new approaches for the development of new aircraft. Based on this scenario, this manuscript describe the efforts to develop a flight simulation-engineering center based on a robotic motion platform. This promising configuration might contribute to overcome some of the previous problems due to augmented motion platform workspace. However, the limited robot payload capacity and the need for a commercial jet representative cockpit, generate critical design constraints and technological challenges to implement this configuration. This manuscript details the design strategy to build the flight simulator assisted by a robotic motion platform and also analyses possible applications.

© 2019, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.This paper presents the SIVOR project, an anthropomorphic-robotic flight simulator under development at the Aeronautics Institute of Technology (ITA), discussing the contribution of an additional 7th degree of freedom (DOF) provided by a linear unit to improve the pilot perception inside the flight simulator. In this context, starting from a canonical washout filter (CWF) implementation, a model-based comparative evaluation – regarding the pilot sensation – is performed considering (i) models of the robotic system with and without the linear unit, (ii) modified versions of the motion-cue algorithm (MCA), (iii) and perception models of the human vestibular system. Such integrated model is used also as the first verification for a predefined flight mission. The results obtained so far suggest an improvement on the representation of the linear acceleration as a larger workspace is provided, though also highlighting the need for further developments on the MCA structure for a better usage of the near feature.

© 2019, Journal of Aerospace Technology and Management. All rights reserved.This paper presents a detailed analysis about the implementation of a washout filter on the SIVOR (Simulador de Voo Robótico – Robotic Flight Simulator) project. The main objective of this project is to develop, on an anthropomorphic robot, a flight simulator which can be used as an Engineering Development System (EDS) and a pilot training platform, capable of providing feelings the pilot would only have in more intensive maneuvers, such as losses/gains of G in aircraft flight tests. The SIVOR project also has the objective of providing a cost-efficient and flexible tool that can be used during the design phases of aircrafts. One of the demanded features of such simulator is a representative behavior of its motion system, which is achieved by an adequate implementation of the washout filter. To the best knowledge of the authors, there are no works in the literature that present a detailed discussion about the implementation of a classical washout filter in such flight simulator, especially when the translational channel is used to its limits. Experimental results to support the proposed solutions are presented herein.

© 2018 Elsevier LtdThe main standards for quantifying waveform distortions in power systems are based on the Discrete Fourier Transform (DFT) through the use of a rectangular time-window of fixed length. However, limitations and imprecisions of the DFT related to the analysis of time-varying signals, typical of environments with renewable sources, have been reported in the literature. This study presents a methodology for identifying the most appropriate time-window length to quantify the emissions of harmonics and interharmonics, considering time-varying signals. The methodology in question is substantiated on the calculation of the harmonic and interharmonic distortions using the DFT according to IEC 61000-4-7 and employing the spectral components acquired from the application of the Prony method and Kalman Filter. It is tested in view of the current signals measured in a real grid-connected photovoltaic installation. The methodology proposed in this work improves the accuracy of the harmonic and interharmonic quantification process using DFT by selecting a proper time-window length, and in addition, identifies the error attributed to the use of a 200 ms time-window length, as premised by the IEC 61000-4-7.

© The Author(s) 2018.Nowadays, it is practically impossible to develop a complex project without the assistance of a comprehensive set of modeling and simulation tools. In space engineering, they are used throughout the product design cycle, from component up to the system level. In conceptual, pre-phase A studies of a space mission, these tools are essential to explore more broadly the design space, in the search for suitable candidate system solutions for the mission. They are also of prime importance in helping to reduce the design time in integrated concurrent design environments. Here, a multidisciplinary tool for concept of operation simulation, developed to be used in that kind of environments, is presented. FOrPlan has the main purpose of performing functional simulations of the satellite and associated ground segments, providing a dynamic verification of the mission designed operational concept. Through the use of suitable graphical interfaces, key parameters of the mission functional scenarios can be presented to the design team and other mission stakeholders, allowing them also a better understanding of the mission operational concept. The simulator presents high flexibility such that it can be quickly customized to different mission scenarios. It has been used successfully at the Space Missions Integrated Design Center (CPRIME) of the Brazilian National Institute for Space Research. In this article, the structure of FOrPlan is presented, and its main features highlighted through results of concept of operation simulations performed for a scientific space mission study that was carried out recently at CPRIME.