Multipole moment preserving condensation of volumetric acoustic sources

A meshfree multipole moment preserving condensation (MmMPC) method is proposed to spatially condense the volumetric quadrupole sources based on Lighthill's acoustic analogy that are extracted from computational fluid dynamics (CFD) data. The purpose of the method is to reduce both the amount of data that must be stored during the CFD analysis and the number of acoustic sources driving the subsequent acoustic propagation analysis, while preserving the accuracy of the predicted sound pressure field. The method uses a distribution of particles with quintic kernels to integrate the acoustic sources and employs a multipole expansion of the harmonic free-field Green's function to preserve the multipole moments of the underlying acoustic sources. The directivity of the sound pressure field due to the quadrupole sources are presented for the first four harmonics of the vortex shedding frequency for flow past a circular cylinder with Reynolds number, Re_D=100 and Mach number, M=0.02. Using the MmMPC method, the number of acoustic sources is reduced by a factor of 120 with the associated far-field sound pressure levels within 0.5 dB of the non-condensed results for all four harmonics.