风洞实验中机翼振动对气动特性影响的计算分析

Numerical analysis of the effects of wing′s oscillation on its aerodynamic characteristics in wind tunnel tests

通过求解非定常N-S方程研究了弹性机翼在低速气流中振动时的气动特性,并与刚性机翼气动特性做了比较。通过结构有限元方法计算出模型机翼的结构模态和相应振动频率,假设机翼以最小刚度的弯曲模态振动,计算了不同振幅下不同迎角、尤其是失速迎角附近的升力特性。计算结果表明,在小振幅下机翼的平均升力特性和刚性机翼相差很小,但当振幅达到一定幅度后,振动机翼下平均升力特性与刚性机翼的结果有较明显的差别,主要表现在最大升力系数的降低和失速迎角的减小。此结果可以解释实际风洞实验中最大升力系数往往小于CFD结果、实验中最大升力系数对应的迎角也比CFD结果小的现象。

The average aerodynamic characteristics of an oscillating wing in low speed flow have been investigated by solving the unsteady N-S equations and compared with that of the rigid wing.The structural modes and corresponding frequencies have been obtained by making use of the Finite Element Method（FEM）.Assuming that the wing takes the first-order mode as its form of movement,the computations have been conducted at various angles of attack and amplitudes and the results have been studied carefully.The following conclusion has been reached： the average aerodynamic characteristics of the wing undergoing slight oscillations don＇t show any significant difference from that of the rigid wing,but with the growing amplitudes of the oscillations increasing differences between these two sets of results show up,showing growing decreases in the maximum lift coefficients and stall attacks.The results presented in this paper have partly explained the fact that the maximum lift coefficient and stall attack in wind tunnel tests are usually smaller than the CFD results where the wing is considered rigid.