A numerical investigation on effects of structural flexibility on aerodynamic far field sound

Abstract

A comparative study of aerodynamic sound from flexible and rigid bodies under the interaction of vortex wake is presented in this work. A bluff body with a trailing splitter plate in a low Reynolds number and low Mach number flow is considered for generation of sound. The vortices are generated by the upstream bluff body, which in turn excites the trailing plate. The objective of the study is to investigate the effect of structural flexibility on the aerodynamic sound. The trailing plate is initially considered to be rigid and then flexibility is introduced to study the influence of flexibility of the plate on the far field acoustics. Three different test cases are considered: a square block with rigid splitter plate, square block with flexible splitter plate and square block without splitter plate. A two-step computational aeroacoustic (CAA) hybrid method is used for computing aerodynamic sound. To account for a bi-directional interaction between the flexible plate and flow field, a two-way fluid structure interaction model is used for the flow simulation. The acoustic propagation is simulated by surface source method based on the Euler equations, wherein the surface source term is determined by transient compressible flow simulation. It is observed that incorporation of flexibility produces significant influence on vortex field and has subsequent effect on far field aerodynamic sound. A higher sound pressure and a changed directivity pattern are observed for the case of flexible plate compared to the case of rigid plate. The results of the study reveal the importance of the flexibility of structure in the character of the far field sound.