Similarity of a Wall Jet with Uniform External Stream and Downstream Suction

Abstract

The two-dimensional turbulent wall jet in the presence of an external stream and downstream tangential suction at zero and adverse pressure gradients was experimentally studied. Streamwise velocity measurements show that the outer regions of the velocity profiles are practically self-similar with or without suction when the ratio of the maximum local and external stream velocities is less than 0.8. Self-similarity is lacking in the inner region and is likely due to viscous friction at the wall hampering flow equilibrium. While the effect of downstream suction is negligible on the mean velocity profiles, the turbulent intensity profiles show that such suction reduces the turbulence level of the flow even far upstream of the suction slot when the streamwise pressure gradient is zero. With the adverse pressure gradient, this stabilizing effect of suction is inhibited. Both the imposed adverse pressure gradient and increasing jet Reynolds number result in a flow nearer equilibrium.