翼型前缘变形对动态失速效应影响的数值计算

Numerical Calculation Effects of Deforming Leading Edge on Airfoil Dynamic Stall Control

翼型或机翼的动态失速效应所引起的低头力矩和正气动阻尼限制了飞行器气动性能的提高,甚至可能诱导发生不稳定运动。应用于小尺寸机翼的前缘动态变形(DDLE)技术,通过实时改变前缘形状,能够改善翼型前缘区域的速度梯度,进而抑制动态失速效应。采用转捩剪切应力输运(SST)黏性模型结合分区混合动态网格技术,研究了这种前缘变形对机翼俯仰运动所引起的非定常流动的影响,得到通过小幅度前缘变形抑制和延迟动态失速的方法,从而提高翼型的气动性能。翼型NAC A0012的数值模拟结果与动态失速风洞试验结果比较表明:所使用的数值计算方法能够较为准确地模拟翼型在动态失速过程中升力系数与俯仰力矩系数的变化情况,可用于研究前缘变形对翼型俯仰运动所引起的非定常流动的影响。前缘动态变形翼型俯仰运动过程的非定常流场的数值模拟表明:在大迎角下不同幅度的前缘下垂运动能够抑制流动分离的发生,从而抑制动态失速,但在大迎角下小幅度高频率的前缘下垂变形能更高效地抑制动态失速;前缘变形幅度以及变形沿中弧线的分布对升力系数和俯仰力矩系数的影响并不明显。

The nose-down pitching moment and the positive aerodynamic damping caused by the dynamic stall effect of air- foils restrict the improvement of aerodynamic performance of aircraft, even might lead to unstable motions of aircraft. The dynamic deformation of leading edge （DDLE） technology, which could be applied to small size airfoils, is able to improve the velocity gradient of airfoil leading edge by real-timely changing the shape of leading edge, and then suppress the dynamic stall effect. The effects of such deformation of leading edge on the unsteady flow caused by airfoil pitching motions are stud- ied by using a method of combining transition shear stress transport （SST） viscosity turbulence model with partitioned hybrid dynamic mesh, then the method of suppressing and delaying dynamic stall effect by deforming the leading edge with small amplitude is obtained, in order to improve the aerodynamic performance of aircraft. The comparison between numerical sim- ulating results of NACA0012 airfoil and wind tunnel test data of dynamic stall effect shows that the numerical method applied can accurately simulate the lift coefficient and the pitching moment coefficient and be used to study the effect of leading edge deformation on the unsteady flow field. The numerical simulation reveals that the drooping deformation of leading edge with different amplitudes at a high angle of attack could suppress the occurrence of flow separation, and then suppress the dynam- ic stall effect. Exactly, the drooping deformation with small amplitude and high frequency at a large angle of attack would have a more efficient suppression on the dynamic stall effect; the effect of the amplitude of leading edge deformation and the deforming distribution along mean camber line on lift coefficient and pitching motion coefficient is slight.