Effect of mean-flow evolution on sound propagation through non-uniform jet flows

ठ** The effects of a nozzle and an evolving jet on sound propagation are studied. To model the sound propagation through non-uniform 3D axi-symmetric mean flows an adjoint Green function problem is solved in the frequency domain with mean-flow fields determined by a RANS calculation. We begin by discussing how an evolving mean flow and nozzle geometry affect the sound from elementary quadrupole sources, comparing these results with those obtained by solving a simpler Rayleigh-like equation for a parallel mean flow. The implications for modelling the noise of turbulent jets are discussed and results given for two current source models in an acoustic analogy.