On the generation of yawing moment using active flow control

The generation of control moments without moving control surfaces is of great practical importance. Following a successful flight demonstration of creating roll motion without ailerons using differential, lift oriented, flow control the current study is a first step towards generating yawing motion via differential flow controlled drag.A wind tunnel study was conducted on a 21% thick Glauert type airfoil. The upper surface flow is partially separated from the two-thirds chord location and downstream on this airfoil at all incidence angles. An array of mass-less Piezo-fluidic actuators, located at x/c = 0.65, are capable of fully reattaching the flow in a gradual, controlled manner. The actuators are individually operated such that the boundary layer could be controlled in a 3D fashion.Several concepts for creating yaw motion without moving control surface are examined. The ultimate goal is to generate the same lift on both wings, while decreasing the drag on one wing and increasing the drag on the other, therefore creating a yawing moment. Decreased drag is created by effective part-span separation delay while increased drag can be created by enhanced generation of vortex shedding or by highly localized 3D actuation.Detailed measurements of 3D surface pressure distributions and wake data with three velocity and streamwise vorticity components are presented and discussed along with surface flow visualization images. The data provide evidence that yawing moments can be generated with AFC.