大攻角翼型的锁频现象及气弹稳定性研究

Study on Frequency Lock-in Phenomenon and Aeroelastic Stability of the Airfoil at High Angle of Attack

翼型大攻角下涡激振动的锁频问题给飞行安全带来潜在的安全隐患。本文采用非定常雷诺时均N-S方程模拟了翼型在大攻角下的强制扭转振动,对翼型在40°攻角下的锁频振动现象进行研究。基于非定常数值模拟的结果,获得翼型表面振动周期气动功均值判断翼型的气动弹性稳定性。计算结果表明:扭转振动的锁频区间呈“V”形,锁频区间内振动频率较小侧气动功显著增加,涡激振动现象发生,而振幅的增大延迟了上仰过程尾缘涡的脱落,会使得其上表面尾缘附近气动功降低,使振动趋于稳定;相空间重构及递归图可以捕捉到非线性动力学系统锁频及非锁频下的状态差异。

The frequency lock-in during vortex-induced vibration of airfoil at high angle of attack brings potential safety risks to flight safety.In this paper,the unsteady Reynolds-averaged Navier-Stokes equations are used to simulate the prescribed pitching vibration of an airfoil at mean attack angle of 40°,and investigate the frequency lock-in phenomenon during airfoil vibration.Based on the results of unsteady numerical simulation,the aero-elastic stability of the airfoil is evaluated by the average aerodynamic cycle work.The results show that the frequency lock-in region of pitching vibration is“V”shaped,in which the side with smaller vibration frequency has higher aerodynamic work,indicating risk of the vortex-induced vibration phenomenon.The increase of vibration amplitude delays the shedding of the trailing edge vortex during pitching,which reduces the aerodynamic work near the trailing edge of the upper surface and promotes the vibration to be stable.Phase space reconstruction and recurrence plots can capture the state difference of nonlinear dynamic system between frequency lock-in and unlock-in.