小攻角对后掠机翼边界层稳定性及转捩的影响

攻角是影响后掠机翼边界层横流稳定性的关键参数之一.以NACA0012翼型为研究对象,通过求解三维可压缩Navier-Stokes方程计算了展向无限长后掠机翼的基本流场;通过求解Orr-Sommerfeld方程得到了扰动波的中性曲线及增长率演化曲线,基于线性稳定性理论(LST)研究了攻角对后掠机翼边界层流动稳定性的影响;最后采用转捩预测eN方法进行了转捩预测.研究发现,扰动波的增长在背风面受到抑制,在迎风面受到增强;转捩首先发生在迎风面,当扰动速度为来流速度的0.05%时,转捩发生的N值在6左右,转捩发生的位置在0.1~0.2个弦长之间.

Effect of attack angle on stability and transition in a swept-wing boundary layer

Attack angle is one of the key parameters to the cross-flow instability of swept-wing boundary layers. For swept NACA0012 airfoil with infinite spanwise length, the basic flow field was calculated by solving the three-dimensional compressible Navier-Stokes equations numerically, the neutral curve and the evolution curve of growth rate were obtained by solving the Orr-Sommerfeld equation, the effect of attack angle on the cross-flow stability was analyzed by linear stability theory (LST), and the transition position was predicted by eN method. It is found that, the growth of unstable waves in the leeward is inhibited but enhanced in the windward. Transition firstly occurs in the windward, and the transition position predicted by eN method is about 0.1 to 0.2 of the chord length with the N factor of about 6 when the disturbance velocity is 0.05% of the free-stream velocity.