平均攻角和振幅对振荡翼型气动特性的影响

Effects of Average Attack Angle and Amplitude on Aerodynamic Performance of an Oscillating Airfoil

关键词:  振荡翼型  升力系数  转捩模型  平均攻角  振幅

Key words:  Oscillating airfoil  Lift coefficient  Transition model  Average attack angle  Amplitude

摘要:

采用一种基于[k-ω SST]模型和[γ-θ]转捩模型的雷诺平均N-S方程数值方法，对雷诺数Re=1.35×105下的NACA0012振荡翼型和静态翼型非定常流场和升力特性进行模拟，在缩减频率K=0.1的条件下研究了翼型振荡运动中平均攻角和振幅对平均升力系数的影响，并与静态翼型的升力特性及实验结果进行了对比。结果表明:当平均攻角小于临界攻角时，翼型的振荡运动会降低平均升力系数，当平均攻角大于临界攻角同时最小攻角小于临界攻角时，翼型的振荡可以提高平均升力系数。在平均攻角为12°～17°时，翼型振幅为6°左右时可获得最大平均升力系数，与静态翼型相比，平均升力系数可提高30%～45.7%。当振荡过程中最小攻角对应静态翼型轻失速攻角时，翼型上仰阶段前缘涡的产生和集中涡的稳定附着是平均升力系数大幅度阶跃式提升的原因，静态翼型与振荡翼型的组合可提高升力并拓宽攻角范围。

Abstract:

The Reynolds average N-S equation enclosed by [k-ω SST] turbulence model and [γ-θ] transition model is adopted to do the numerical simulation for the unsteady flow field and lift characteristics of oscillating and static NACA0012 airfoils. The effects of average attack angle and amplitude on the average lift coefficient are studied in the case of Re=1.35×105 and K=0.1，which is compared with lift characteristics of static airfoil and experimental values. The results show that the oscillatory motion of airfoil will decrease the average lift coefficient if the average attack angle is less than critical angle. And it will increase the average lift coefficient under the condition of the average attack angle greater than critical angle，while the minimal attack angle less than critical angle. In the range of 12°～17°，the oscillating airfoil with amplitude of 6°can provide a better average lift coefficient compared with the static one，and the improvement value is about 30%～45.7%. When the minimal attack angle located in the light stall range of static airfoil，the average lift coefficient will step up during the process of generation of the leading edge vortex and concentrated vortex adhering on the pitching up airfoil. So the combination of static and oscillating airfoils could provide high lift and extend critical angle.