LES studies on the correspondence between the interaction of shear layers in post-reattachment recovery and in a plane turbulent wall jet

摘要

Turbulence budgets, extracted from highly-resolved LES, are used to contrast the turbulence characteristics of the flow behind a backward-facing step with those of two wall jets, one bounded by a real wall and the other by a frictionless wall, thus allowing wall-blocking effects to be isolated from those of near-wall shear. The objective is to identify common features in the turbulence processes associated with the interaction between the near-wall region and the outer layer of the separated flow and the wall jet, and thus isolate mechanisms possibly responsible for the poor representation of the post-reattachment recovery returned by most of RANS closures. The budgets show that certain regions of the separated flow present similarities with the wall-shear-free jet, while others share features with the real wall jet. Turbulent transport by third moments and pressure-velocity correlations are shown to be important processes in the interaction between the near-wall region and the outer layer.