Acoustic Signature of Square Cylinder in a Compressible Flow

Abstract

The Aeolian tones radiated from structures are important in various engineering fields. For example, in military and defense applications, it is used for detection and survivability. Aeroacoustic noise is increasingly used as a critical design variable in modern engineering designs. This in turn has led to an increase in the research efforts aimed at numerical prediction of aerodynamic noise, often dubbed computational aeroacoustics (CAA). A numerical study of aerodynamically generated acoustic noise was carried out. Simulations of 2D, laminar, and compressible, viscous flow were performed at Reynolds Number (Re) ∈ [60, 200] and Mach no. (Ma) ∈ [0.2, 0.4]. Roe Flux-Difference Splitting Scheme was used to solve the governing equations with finite volume differencing. The Least square cell based spatial discretization scheme was used with second-order upwind scheme for calculating convection terms. Acoustic calculations were done using Ffowcs-Williams and Hawkings (FW-H) formulation. The peak in the receiver spectra matches the dominant frequency in the lift force history. Sound Pressure level decreases with decreasing flow velocity and Reynolds number. Acoustic peak frequency shifts toward higher frequency value with increasing Mach number for all cases of Reynolds number. The sound pressure level was observed to be higher downstream of the flow. Wide band noises at frequencies higher than the fundamental frequency were observed to be the subharmonics of the fundamental frequency of sound.