RPM - the fast Random Particle-Mesh method to realize unsteady turbulent sound sources and velocity fields for CAA applications

Abstract

The simulation of broadband noise with CAA techniques is discussed. Unsteady broadband sound sources are modeled in the time-domain with a highly efficient computational method. The generated fluctuations reproduce very accurately autocorrelations and integral length-scales such as that provided by a RANS simulation of the time-averaged turbulent flow problem. It is argued that an approach based on synthetically generated sources has to be seen as an algorithmic extension of traditional statistical broadband methods in the frequency domain. Fluctuating quantities are generated by spatially filtering convective white-noise. The discrete realization of convective white-noise is based on random particles that are advanced using an area-weighted mean of the mean-flow from neighboring mesh points. The spatial filtering is realized by interpolating the random values with a particle shape function onto the neighboring mesh points and applying subsequently a sequence of 1D filtering operations. Sample results for different aeroacoustic applications of the method are presented.