HYBRID FLOW CONTROL TECHNOLOGY BASED ON VARIABLE CAMBER AND CO-FLOW JET

Modern aircraft emphasizes the characteristics of high-speed cruise and stealth. As a result, the airfoil used usually has a relatively small thickness, a small leading edge radius and less camber. The performance of such airfoils is poor, with early flow stall at a low speed condition, and resulting in the limitation of the STOL characteristic and weight-carrying capacity of the aircraft. Thus, it is necessary to improve the aerodynamic performance of airfoil by using active flow control or passive flow control. In this paper, the innovative co-flow jet (CFJ) technology is investigated, which is coupled with variable camber technology (including the trailing-edge flap and leading-edge droop) and flow mechanism, as well as control efficiency of so-called hybrid flow control approach. As shown by numerical simulation results, a single flow control technology cannot improve the lift of the thin airfoil substantially. Nevertheless, the combination of CFJ with variable camber technology could realize the advantages of both technologies (e.g. the delay of trailing edge stall induced by CFJ, the delay of leading edge stall caused by droop nose, the decrease of zero-lift angle induced by trailing edge flap, etc.). The combination scheme of CFJ and variable camber technology in this paper could yield the maximum lift coefficient of C_Lmax=3.3127, 96% higher than that of the original airfoil, implying that the hybrid flow control technology has valuable potential for aviation industry application.