Computation of Aeroacoustic Sound Via Hybrid CFD/CAA-Methods.

摘要

Different formulations for a two step CFD/CAA approach are investigated. The acoustic field is simulated using linearized perturbation equations which are excited by sources determined from the unsteady compressible near field flow. The sound generated by a cylinder in laminar at Mach number M=0.3 and Reynolds number Re=200 is used as a test problem. It is examined whether the viscous/acoustic splitting method of Shen et al., which is based on a simulation of the incompressible flow field, can be adapted to a compressible base flow simulation. It is found that excessive artificial vorticity is generated in the wake of the cylinder due to the excitation of hydrodynamic instabilities. A new set of governing acoustic perturbation equations (APE) is proposed, which includes sources determined from a compressible flow simulation. As shown for the test problem, the occurrence of vorticity is prevented completely since the source solely excites acoustic modes in the APE.