A-priori studies of a near-wall RANS model, within a hybrid LES/RANS scheme

Abstract

This chapter examines the behavior of a one-equation, turbulence-energy-transport model by coupling Reynolds-Averaged Navier-Stokes (RANS) near-wall model to the large eddy simulation (LES) domain in a fully developed channel flow. The study illustrates the difficulties encountered when the interface location is chosen arbitrarily, without reference to grid-related criteria, and when the subgrid-scale model is of a different type to the RANS model used in the near-wall layer. The latter usually gives rise to high levels of modeled turbulent transport in the presence of unsteady motion that is of usually the same order as that returned by the LES solution in the same region. The response of the model is considered when it is subjected to the LES solution at a prescribed distance from the wall. Further, the chapter discusses coupling criteria given the desirability of freedom of choice of the subgrid-scale model in the LES domain and in locating the interface. Initial efforts towards a fully coupled hybrid solution are also presented.