Influence of the shear layer thickness on the flow around unsteady airfoils

Abstract

Experiments with a pitching and plunging unsteady airfoil have been conducted in order to investigate the influence of the separating shear layer properties on the formation and detachment of leading edge vortices (LEVs). The chord length was varied from 90 to 180mm keeping all non-dimensional parameters constant. It has been shown, that themechanism of vortex detachment changes with chord length, manifested by a change in flow topology. One mechanism scales with chord length, the other is attributed to viscous effects in the boundary layer. For this mechanism a new scaling of the LEV circulation is introduced.