Experimental research on three-axis control of flying-wing aircraft based on active flow control

The flying-wing aircraft has excellent aerodynamic efficiency and stealth performance. However, due to the lack of tails, the flying-wing aircraft has a serious attitude control problem. In this paper, the effective flow control strategy of three-axis control is proposed by using continuous jets for a flapless flying-wing aircraft. The wind tunnel test of two kinds of flying-wing models, namely one flow control model and one mechanical control model, is conducted, and the control effect is analyzed and compared. By simultaneous blowing of the circulation control actuators inboard and differential blowing of the circulation control actuators outboard, the pitch and roll controls are achieved, respectively. It also has an effective control effect at very large angles of attack where the conventional control surface fails. A linear relationship is found between the increment of the controlled aerodynamic force/moment coefficient and the momentum coefficient for circulation control actuators. Moreover, to resolve the difficulty in yaw control, a novel wingtip jet is proposed based on the concept of the all-moving tip and compared with apex jet and circulation control jet. It is found that the wingtip jet is the most efficient actuator, followed by the simultaneous-blowing circulation control jet. Therefore, based on the research above, two optimized fluidic control configurations are proposed. One employs circulation control jet and wingtip jet, and the other is completely dependent on circulation control jet. Finally, the flow control mechanism of circulation control is discussed. Circulation control significantly accelerates the flow on the upper surface of the airfoil in attached flow and reduces the flow separation region in separated flow, leading to aerodynamic performance improvement. These results provide an important theoretic basis for the flapless flight control of flying-wing aircraft.