Modelling of sound propagation through non-uniform flows of turbulent jets

The paper is devoted to a new hybrid approach for solving a linear sound propagation problem for application to subsonic jet mixing noise. The linearised Euler equations in the frequency domain are solved by using a vector Green's function technique to obtain the far-field noise prediction. The Green's function is obtained numerically by solving an adjoint linearised problem in the jet near-field using appropriate "non-reflecting" boundary conditions. The boundary value problem in the frequency domain is solved with a finite-difference method and an explicit pseudo-time-stepping scheme. It is shown that the numerical artifacts in the solution due to the shear layer hydrodynamic instability can be suppressed by using a dual-scale pseudo-time-stepping scheme. Two semi-empirical acoustic source models are considered and sound prediction results for a benchmark round jet problem are presented.