Abstract
To specify the effect of upstream pressure gradient on the mean velocity profiles of a separating flow, Couette type foward-facing step flow, whose upstream flow is the fully developed plane channel flow between moving and stationary walls, is investigated. The stationary wall has a step and the resultant channel contraction ratio (CR) is 0.75. The upstream flow is set as pure Couette (β_0 = 0) or pure Poiseuille (β_0 = -1)turbulence channel flow, where β_0 is the upstream flow type parameter. The upstream Reynolds numbers based on the friction velocity and upstream channel half width are about 300. Velocity profiles are measured with hot-wire anemometry at sections of x/H = -30,10,20,30 and 50. The distributions of pressure coefficient shows that the upstream flow is the Couette flow with negligible streamwise pressure gradient. The downstream mean velocity distributions of Couette and Poiseuille type flows reflect the continuity amstraint. Turbulemce instensity distributions show the effect of different flow type parameter.
