Design of Active Flow Control at a Drooped Spoiler Configuration

Abstract

The contribution discusses the implementation of active flow control with vortex generator jets into a (nominally) 2D two-element high-lift airfoil configuration featuring a drooped spoiler. The vortex generator jets—local air-jets producing a longitudinal vortex inside the boundary layer and thus having a positive influence on the separation behavior—are integrated upstream of the droop-spoiler hinge line. Therefore they are able to prevent a separation at the kink, which allows larger downward deflection of the spoiler and thus higher overall maximum lift. The setting of the high-lift flap has been optimized by a differential evolution algorithm utilizing numerical methods, including the spoiler droop, to acquire the cost function. Also the optimization considers the effect of the vortex generator jets on the local boundary layer by a so-called statistical model, which is calibrated to represent one certain jet orifice configuration. The numerical results are compared to and validated with numerical solutions fully resolving the vortices. It will be shown that vortex generator jets in such application have a significant potential to increase the maximum lift. The use of the statistical model for the vortex generators is a key to enable optimization studies of the flap and spoiler setting including the positive effect of the vortices. It will be shown that the full potential of application of this active flow control technique only appears if such optimization studies can be done.