DOI: 10.1615/TSFP6
MASSIVE SEPARATION OF TURBULENT COUETTE FLOW IN A ONE-SIDED EXPANSION CHANNEL
摘要
Direct numerical simulation has been performed to study wall-driven flow over a backward-facing step at Reynolds number Re = 5200 based on the step height h and the upper wall velocity Uw. The flow configuration consisted of a step with height equal to that of the upstream channel yielding an expansion ratio 2:1. The instantaneous enstrophy contours revealed the formation of Kelvin-Helmholtz instabilities downstream of the step. A fully redeveloped Couette flow cannot be reached in the downstream part of the channel due to mass conservation. The local wall pressure coefficient gave evidence of an adverse pressure gradient in the recovery region where a Couette-Poiseuille flow type prevailed. The budgets for the Reynolds shear-stress and turbulent kinetic energy have been computed. In the mixing layer, the peak production of turbulent kinetic energy was 2.5 times larger than that of viscous dissipation.