Acoustic scattering by 3D elastic plates of composite materials

Resumo

© 2018 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.This work presents a study of acoustic scattering by 3D elastic plates made of composite materials. A fast multipole boundary element method is employed to solve the Helmholtz equation subject to boundary conditions consisting of the vibration of the elastic plate. Such boundary conditions are obtained by the solution of a structural modal basis which satisfies the free vibration problem of plates composed of orthotropic materials. The fluid-structure interaction problem is coupled through the linearized Euler equation. An important difference between the composite and aluminum plates is observed in terms of the specific mass, which impacts the fluid-structure coupling. Results demonstrate that the higher frequency propagation of bending waves along composite plates leads to a further noise reduction when compared to elastic aluminum plates. Solutions obtained by twodimensional plates are compared to those obtained by fully three-dimensional ones. It is shown that the 2D models of composite plates cannot recover the directional aspects of trailing-edge noise scattering by 3D plates due to the spanwise effects of propagation of bending waves that impact on the acoustic solution.