Fast computational aeroacoustics using random distributions of Kirchhoff's spinning vortices with application to sibilant sound generation

Hybrid approaches to low Mach number computational aeroacoustics (CAA) for three-dimensional problems have a high computational cost and often demand resorting to supercomputing facilities. The bottleneck concerns the first step of the process, in which a computational fluid dynamics (CFD) simulation is carried out to solve the incompressible Navier-Stokes equations, to obtain the source term for the acoustic wave equation. In this work we suggest that, for some problems in which average results are only needed, it may be possible to avoid the CFD simulation and approximate the flow noise sources by means of a random distribution of Kirchhoff's spinning vortices. In this way, one simply needs to solve an acoustic linear wave operator to solve the aeroacoustics problem. We have applied such methodology to simulate the generation of the sibilant sound /s/ on a realistic geometry for which CAA and experimental data exist. After validation, the versatility of the proposed approach is tested on a simplified geometry, which may be useful to synthesize more complex sound in the future, like syllables. Implementation details of the vortex distribution in a stabilized finite element (FEM) code are also discussed.