Wall-Modeling in Complex Turbulent Flows

Resolution of wall layer turbulent structures in large eddy simulation of high Reynolds number flows of aeronautical interest requires inordinate computational resources. LES with wall models is therefore employed in engineering applications. We report on recent advances at the Center for Turbulence Research (CTR) in the development of wall boundary conditions for complex turbulent flows computed on unstructured grids. We begin by describing a novel application of wall modeled LES to a high lift airfoil system. This flow field is very complex involving boundary layers, free shear flows, separation and laminar/turbulence transition. We then describe a non-equilibrium model that requires the solution of the full 3D RANS equations in the near wall region. This model is successfully applied to a spatially evolving transitional and a high Reynolds number flat plate boundary layer. Finally we describe a new approach to LES using differential filters. An important byproduct of this approach is the derivation of slip velocity boundary conditions for wall modeled LES. This methodology is successfully applied to flow over NACA4412 airfoil at near stall conditions.