Jet-noise reduction by streak-generating tabs: Coherent structures in the velocity field

Abstract

© 2024, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.The present paper is a follow up of a previous study on the effect of streaky-generating cylindrical tabs located on the inner surface of a round nozzle on jet aeroacoustics (Amaral et al., AIAA AVIATION 2023 Forum, p. 4516, 2023). The aim is to identify coherent structures through stereoscopic particle image velocimetry (stereo PIV) measurements obtained in crossstream planes parallel to the jet nozzle exit. As the tabbed nozzle has L-fold symmetry, Floquet exponents are used to perform Fourier decomposition in the azimuthal direction. Spectral proper orthogonal decomposition (SPOD) is employed to extract coherent structures. Comparison of the structures obtained for nozzles with and without tabs show the strong enhancement of streaks produced by the tabbed nozzle.