Study of acoustic reflection and diffraction using boundary integral equations

Abstract

Noise regulations have become incrementally more stringent as air traffic has increased and will likely continue to do so in the future. In the last three decades, significant jet noise reduction has been achieved due to efforts on the design of more efficient and quieter engines. Since then, airframe noise associated with the unsteady flow around the aircraft has become a significant source of noise, specially for landing configurations. Therefore, the investigation of the physical mechanisms of acoustic reflection and diffraction which occur in the presence of flows along aerodynamic configurations is of paramount importance for understanding acoustic propagation effects in airframe noise. The present work concerns the study of the effects of acoustic reflection and diffraction using boundary integral formulations. A numerical tool that solves the Boundary Element Method, BEM, formulation will be developed in order to investigate the problems of interest. The Helmholtz equation will be solved with the capability of including non-linear quadrupole sources. These aeroacoustic sources will be calculated from numerical simulations of aerodynamic flows using a computational fluid dynamics tool available in the present research group. The quadrupole sources will provide the incident acoustic field along the solid geometries present in the flow simulations. An investigation of the effects of acoustic reflection and diffraction will be presented in order to calculate the dipole sources forming along the solid geometries in the flow. Furthermore, the BEM numerical tool will be used for verifying other numerical solutions of reflection and diffraction along complex geometries, obtained by a finite difference formulation.