Numerical studies on turbulent free-shear and wall-bounded flows with application to acoustics

Numerical simulations of turbulent free-shear and wall-bounded flows are performed. Comparative studies between different approaches of turbulence modeling such as unsteady Reynolds Averaged Navier-Stokes (URANS), Detached-Eddy Simulation (DES) and a new approach known as Partially Averaged Navier-Stokes (PANS) are carried out for flow over a smooth square cylinder and a backward facing step. It is shown that under the same computational grid resolution, results from PANS simulations show superior scale resolution (both in time and space) when compared to URANS and DES results. Moreover, PANS results are in better agreement with experimental data when compared with DES and URANS. A grid resolution study reveals that when using PANS, smaller turbulent scales of motion are resolved using a fine grid.; For the flow over a smooth square cylinder, the pressure fluctuations in the near field show that PANS results contain a broad spectrum of frequencies compared to URANS and DES. The acoustics radiation from the near field and its propagation into the far field is predicted in this work using Ffowcs-William and Hawkings (FW-H) equation. The power spectral densities (PSD) of the far field pressure show similar characteristics as those obtained in the near field analysis.; Through this set of studies, PANS has been shown to be a very powerful turbulence modeling tool for unsteady flows and can be used for both acoustic radiation and structural vibration.