Oscillation Effects on Boundary-Layer Development Under the Influence of Favourable Pressure Gradients

Abstract

An experimental study has been conducted to investigate the effects of oscillation at a range of Strouhal numbers (0.0006 to 0.0113) on the boundary-layer development of a flat plate under the influence of favorable pressure gradients. The Reynolds number was 10 6 based on the flat-plate chord length. An inverted airfoil placed in the turbulent region over the flat plate was used to create the effects of favorable pressure gradients. Hot-wire anemometry was used to measure the velocities in the streamwise direction. The flow separates near the rounded leading edge, causing the formation of the separation bubble. It is found that the time-averaged velocity and turbulence intensity profiles remain mostly unaffected by oscillation in the turbulent flow regions (II and III). The boundary-layer properties such as the boundary-layer displacement thickness, momentum thickness, andthe shape factor remain almost constant. However, in region I, in which the flow is in its transitional state, oscillation slows the reattachment process under the influence of favorable pressure gradients.