Similarity study of the wall-jet-flow outer region

Abstract

The similarity profiles of the two-dimensional turbulent wall jet in the presence of a freestream and tangential suction at zero and adverse pressure gradients were studied. A previous study1 shows that the outer regions of the velocity profiles are practically self-similar for values of the ratio of the free-stream and maximum local velocities (Uj/U m) less than or equal to 0.8. A complimentary study on the similarity of the outer region by varying the ratio of jet to free-stream velocities (Uj/U∞) and by altering the ratio of the blowing to suction slot width (b/bs) are presented in this paper. The results show that, to effectively implement the wall-jet concept for overcoming flow separation, the ratio of jet velocity to free-stream velocity U j/U∞ should be equal to or greater than 2. This ratio seems to vary proportionally to the test section divergence angle used to generate the adverse pressure gradient. Additionally, the width of the jet slot and the jet flow rate are important parameters for obtaining the high ratios of Uj/U∞ required for a wall-jet to effectively control flow separation when implemented in high-lift devices. Copyright © 2009 by Temasek Laboratories, National University of Singapore.