Determination of SPL From a Jet Exhaust Using Computational Fluid Dynamics

A round, compressible, turbulent cold jet exhaust at a Mach of 0.9 was numerically simulated in ANSYS Fluent. Grid independence test was done and a mesh containing 2.5 million cells was selected to carry out the three-dimensional calculations, using three different turbulence models:
$\mathrm{k}-\omega,\ \mathrm{k}-\epsilon$
, and Reynolds Stress Model. Axial variation of the mean flow velocity and axial variation of Reynolds stresses at the jet centerline, numerically obtained by solving the Reynolds-Averaged Navier Stokes (RANS) equations, were validated against the experimental trends already available in literature. The results from the CFD analysis of the nozzles themselves were also verified against an analytical model developed in MATLAB. The most accurate results were obtained using the Reynolds Stress Model, which were used along with the Ffowcs Williams-Hawking equations to calculate the far-field Sound Pressure Levels (SPL). It was concluded that the absolute values of SPL obtained from the URANS calculations were not comparable to the experimental data, however, the trends in SPL were reasonably well-predicted.