Experiments in the control of wing rock at high angle of attack using tangential leading edge blowing

Supermaneuverability of highly swept delta wing aircraft requires operation in regions of the flight envelope where very high angles-of-attack are encountered. In these regions, the vortical flow on the lee-side of the wing characteristic of highly swept wings at low to moderate angles-of-attack becomes highly unsteady and disappears completely. Conventional control surfaces operating in the wake of such stalled flow are incapable of generating the necessary forces and moments to control the aircraft.; The present investigation is motivated by the success of recent research in the use of thin, high momentum jet sheets blown tangentially along the wing leading edges as a means to reestablish and to control directly the vortical flow at post-stall angles-of-attack. It is found presently that a good strategy for generating linear roll control torque is to first blow symmetrically, i.e. blowing equally along both leading edges of the wing. This produces a controllable attached flow. Then by asymmetrically increasing the blowing strength along either the left or the right leading edge, positive or negative rolling moment is generated. It is this resultant rolling moment that is used to control the rolling motion of the wing.; A parametric semi-empirical aerodynamics model is developed to simulate the static effects of tangential leading edge blowing on both the vortical flow field and the resulting wing rolling moment. Parameters of the model are identified from experimental data by means of a least-squares parameter identification method. The completed aerodynamics model is coupled with a one-degree-of-freedom dynamics model to simulate the natural, i.e. wing rock, and the controlled wing rolling behavior. Fidelity of the parametric models is verified by comparing simulated roll responses with experimental wind tunnel data.; An active feedback control algorithm is designed to regulate the amount of asymmetric blowing to achieve roll control. The effectiveness of tangential leading edge blowing as a roll control device is demonstrated experimentally in wind tunnel tests by the stabilization of a delta wing model which underwent wing rock at an angle-of-attack of fifty-five degrees.