涡襟翼在不同雷诺数下的控制分离特性研究

受鸟类抬起羽毛控制分离流的启发，涡襟翼成为翼型大迎角分离流的控制措施之一。采用数值模拟方法研究不同雷诺数下涡襟翼在控制翼型大迎角分离流动时的气动特性及其物理机制。结果表明：涡襟翼在低雷诺数下能够极大地改善翼型的大迎角升力特性，其物理机理是涡襟翼将翼型主分离涡的涡心位置控制在离翼型更近的区域，且涡心位置的涡量得到大幅提升，使得涡心附近的低压特性影响到翼型上表面，而且涡襟翼能够将翼型上方前区的低压与下游的高压隔开；但是在高雷诺数（对应常规飞机雷诺数）下涡襟翼改善翼型大迎角气动特性的效果远不如低雷诺数情况，由此解释了为什么鸟类能够通过羽毛抬起提高升力特性，而常规飞机的涡襟翼只能作为阻力板使用的原因。

Research on the Control Separation Characteristics of Vortex Flap under Different Reynolds Numbers

Inspired by birds raising their feathers to control the separation flow, vortex flap has become one appoach to control the separation flow over airfoils at high angles of attack. In this paper, the aerodynamic characteristics and physical mechanism of vortex flap controlling separation flow over airfoils under different Reynolds number is numerically studied. The results show that vortex flap is able to greatly improve lift of the airfoil at low Reynolds number under high angle of attack. Its physical mechanism is that the vortex flap makes core position of main separation vortex closer to airfoil camparing to original airfoil, and then the low-pressure characteristics caused by th e vortex core will affect the flow field on the upper airfoil surface. In addition, the pressure filed on the upper surface of the airfoil is divided by vortex flap into two parts: the low pressure aera in the front and the high pressure aera at the back. However, under high Reynolds number (corresponding to conventional aircraft Reynolds number), the effect of vortex flap on improving the aerodynamic characteristics of airfoil at high angle of attack is far less effective compared to the case of low Reynolds number. This explains why birds can improve lift characteristics through feather lifting, while vortex flap can only be used as drag plates in conventional aircraft.