Aeroacoustic noise calculation of noncompact bodies with time-domain scattered green’s function

Abstract

In view of the scattering effect induced by non-compact bodies, and the growing time cost of the noise calculation with high-order methods, tailored green function methods gradually become effective means to study acoustic noise of noncompact bodies. With the help of free-space green function and convective wave equation, time-domain integral method is presented to calculate scattered green function under arbitrary boundary condition. In order to verify the present method, the cylinder noise under solid wall condition is firstly calculated with stationary point source. The scattered green functions are in good agreement with Gloerfelt’s analytical solution and Takaishi’s frequency method. The pressure distribution demonstrates that the pressure appears as circle shape at low frequency but petal-like pattern at high frequency. Furthermore, point sources in parabolic moving form is chosen to study the influence of scattering effect to far field noise. Numerical results illustrate that the scattering effect is closely related to cylinder radius and the location of sound sources, large body size and sound sources adjacent closely to body surface could lead to serious scattered noise. Besides, time-domain method overcomes the limit that noise calculations have to be performed in relative coordinate system, and it can calculate scattered noise accurately and instantaneous.