非正弦振型对沉浮翼型推力产生的影响

Numerical Study of Nonsinusoidal Motion Effect on Plunging Airfoil Propulsion

对二维沉浮振荡NACA0012翼型周围流场进行了数值模拟,通过改变非正弦参数K实现了不同的非正弦振型,由此分析了非正弦振型对推力产生的影响。结果表明:非正弦振型主要通过影响瞬时推力系数、最大推力系数和流场结构来影响沉浮翼型推力的产生;较正弦沉浮振动,K大于0时对应的振型可以增加平均推力系数,在一定沉浮频率和幅度下,平均推力系数随K的增加而增大,推进效率随K的增加而降低;振型对流场涡结构有明显的影响,随着K增大,翼型尾缘产生更强的反卡门涡街,从而引起推力系数增大,但K增大会使前缘分离更加严重,导致推进效率降低。

The effect of nonsinusoidal motion on plunging airfoil aerodynamics for thrust generation was numerically studied with a 2-D NACA0012 airfoil at Re = 10^4. A nonsinusoidal parameter K was employed to realize various nonsinusoidal motions. The results reveal that nonsinusoidal motion has a noticeable effect on the aerodynamic performance, as it affects the instantaneous force coefficients, maximum thrust coefficients, and flow structures. An increase in K results in better thrust generation performance at a fixed St, especially for K^0. It is also found that the nonsinusoidal motions have notable effect on the wake pattern, and a larger K induces stronger reverse von Karman vortex in the wake, which in turn leads to the thrust generation enhancement. However, the propulsive efficiency decreases with the increasing K because of the larger scale of leading edge separation caused by the larger K.