Turbulence modelling influence on Ffowcs Williams-Hawkins Acoustic Analogy based CFD simulations for low Mach number turbulent flows

The problem of aeroacoustic noise prediction is today a big challenge for the huge computational effort required to get a state of the art simulation. The use of simplified models is possible in CFD codes but their efficiency is matter of research and discussion. A research has been made to contribute to the understanding of this topic, by focusing the attention on dipole equivalent sources generated by the turbulent boundary layer at high Reynolds Numbers. A test case has been taken, consisting in a low Mach number flow interacting with a square section prism, at Reynolds Number approximately equal to 45,000. The Ffowcs Williams-Hawkins Acoustic Analogy has been used over unsteady CFD simulations. The main purpose of this research is to understand the differences of simplified models respect to a reference Large Eddy Simulation, dealing with high nearwall resolution (till the viscous sub-layer). The simplified approaches considered are relative to a Large Eddy Simulation on coarser nearwall mesh (and the use of Launder and Spalding Wall functions), 2D k-e U-RANS and 2D RNG k-e U-RANS simulations, both on high or coarse nearwall resolution. In this paper capabilities and limits of the different approaches are investigated.