New Flow Control Techniques with Prepositioned Stationary or Vibrating Elliptical Wing at Low Speed and High Angle of Attack

Abstract

Strong coupling of aerodynamics and dynamic motion will occur on advanced highly maneuverable aircraft at a high angle of attack, which makes the complex flow field heavily nonlinear. To improve the aerodynamic performance at a high angle of attack and broaden the flight boundary of the aircraft, a new combination configuration of a prepositive elliptical wing–main wing is proposed. The high-energy wake vortex generated by the stationary or vibrating prepositive wing is mixed with the airflow field of the main wing at the high angle of attack, and the air flow is accelerated through the space between the elliptical wing and its main wing, thereby enhancing the ability of the boundary layer to resist separation. A two-dimensional combined configuration of a stationary or vibrating prepositive elliptical NACA0012 airfoil was designed, and the flow control simulation was studied with a high-precision computational fluid dynamics (CFD) method. The results show that the stationary elliptical wing generates lift by itself, the generated wake suppresses the flow separation on the upper wing surface of the main wing, and the lift-to-drag ratio can be increased by as much as 319%. Moreover, when the prepositive wing vibrates at a small amplitude, the generated wake energy is stronger and the control effect on the separation of the main wing is much more remarkable. In the best case, the lift-to-drag ratio of the main wing can be increased by 485%. Compared with conventional flow control techniques, the new combined flow control method has the characteristics of a simple form and a high degree of control without forming waste resistance, and significantly can improve the flow separation characteristics at high angles of attack and enhance the maneuvering ability of aircraft.