Computational Modeling of the Unsteady Wake Behind Gurney-Flaps

Abstract

The effect of small micro-tabs (Gurney-flaps) mounted at the lower trailing edge of a HQ17 airfoil has been studied using numerical simulation. The focus of attention has been placed on the unsteady flow structures in the wake of the Gurney-flap, as these are responsible for increased induced drag. At a Reynolds number of 106, the flow is investigated using steady and unsteady simulations based on the Reynolds-averaged Navier-Stokes equations (URANS) as well as Detached Eddy Simulations (DES). In order to reduce the occuring unsteady flow structures, further simulations have been performed using alternative trailing edge shapes. The results show that the unsteadyness can successfully be suppressed and the drag can be reduced substantially using advanced flap concepts.