Zonal Overset-LES with stochastic volume forcing

Abstract

In this contribution, a hybrid Zonal LES tool is presented that uses a stochastic volume forcing for “inflow” turbulence generation. The here used hybrid approach is based on an implementation of the Non-Linear Perturbation Equations extended with fluctuating viscous terms, denoted as “Overset” since a perturbation analysis is performed on top of a background flow. A turbulent flat plate is considered to investigate the generation of inflow turbulence and how this artificial turbulence is seeded into the computational domain. At the inflow region, turbulence is stochastically generated (in three-dimensional space and time) with the Fast Random Particle-Mesh method and subsequently injected in the Overset-LES domain with the eddy-relaxation source term. This eddy-relaxation source term is shown to pilot the hydrodynamics while leaving the acoustics untouched (i.e., transparent for acoustic). The application of the Overset-LES method to a NACA0012 trailing edge at zero angle-of-attack is furthermore presented. Mean flow and turbulence characteristics in the wake show a good agreement with experimental data. Finally, a possible way to couple the turbulent sound sources into a CAA simulation is described. Comparison between directivities obtained with this method and reference data revealed good agreement.