Development of non-conventional control methods for high angle of attack flight using vortex manipulation

Experiments were conducted in a low-speed wind tunnel to investigate methods of manipulating the forebody vortices on a generic fighter model to produce controlled yawing moments at high angles of attack. In addition to measuring the forces and moments on the complete configuration, isolated forebody forces and moments were measured to quantify the contributions from the forebody alone. Two schemes of vortex control were evaluated: (1) individually-controlled forebody tip strakes and (2) individually-controlled blowing ports on the forebody. The effectiveness of the forebody strakes in controlling forebody side forces was strongly dependent on the size and location of the strakes. Yaw moment can be produced by deploying the forebody strakes asymmetrically, or can be eliminated by deploying the strakes symmetrically. The most effective strake position was found to be near the primary separation point. Blowing on the surface of the model was shown to have a strong effect on the yaw moment. Blowing either forward or aft in a tangential direction appears to be more effective than blowing normal to the surface. It was concluded that the most effective methods to control the yawing moment on the forebody was to minimize the natural asymmetry with a pair of symmetrically mounted tip strakes and to perturb the vortex system away from the symmetric condition with asymmetric blowing. NOMENCLATURE