Experimental investigation of synthetic jet control of wing rock for a flying wing aircraft

Abstract

Flying wing aircraft easily experience wing rock due to the lack of lateral-directional stability, which causes serious challenges to flight control and safety. Thus, it is necessary to reduce the wing rock amplitude or reduce the mean roll angle by additional control. For a flying wing model with a 65° leading-edge sweep, we propose a strategy using an array of synthetic jet actuators to control the wing rock. The control effect and mechanism are studied by attitude measurement and particle image velocimetry measurement in a wind tunnel; the results confirm that the synthetic jet can effectively change the trim position of the wing rock. The control effect is affected by the angle of attack, Reynolds number, actuation position, actuation voltage, and frequency. In general, downstream actuators perform better at low angles of attack, while upstream actuators perform better at high angles of attack; the actuators positioned at the downward rolling side have a better effect than those positioned at the upward side. Furthermore, continuously variable control of the trim position can be achieved by changing the actuation voltage or modulation frequency, which provides a base for attitude manipulation by using active flow control instead of a mechanical control surface. Quantitative analysis of the flow field indicates that the leading-edge vortex on the upward side provides a rolling moment, while the recirculation zone on the downward side also contributes to the wing rock. This is a dynamic process, causing the flying wing to balance at a nonzero mean roll angle. The synthetic jet positioned at the downward rolling side can transport high-momentum fluids to the near-wall region, thereby suppressing flow separation and reducing the size of the recirculation zone. This enhances the lift on the control side and thus reduces the mean roll angle of the wing rock.