流固单向耦合的能量法及机翼颤振预测

Wing Flutter Prediction Using an Energy Method Based on One-Way Fluid Structure Coupling

为准确预测机翼颤振边界,发展了一种基于流固单向耦合的能量方法。首先,为考虑机翼振动对流场的影响,采用课题组所发展的快速动网格技术更新流场网格;然后,在更新后的网格上采用SIMPLE算法求解基于任意欧拉拉格朗日格式的雷诺时均纳维斯托克斯方程,计算出流场压力。通过机翼表面压力计算机翼的气动力,进而计算机翼的气动功,将气动阻尼等效为黏性阻尼,通过等效黏性阻尼公式计算得到机翼振动的气动阻尼;最后,通过气动阻尼来判断机翼的颤振边界。采用所提能量方法对wing 445.6的气动阻尼进行了分析,并计算了其无因次颤振流速,计算得到的无因次颤振流速与实验值的相对偏差大约为1.5%。研究发现,在跨声速条件下wing445.6的气动阻尼随着模态阶数的增加逐渐增加。通过分析机翼表面气动功的分布发现,在跨声速流动中机翼附近流场的激波是产生正气动功的主要原因,也就是说机翼跨声速颤振主要是由激波引起的。

To predict the flutter boundary of airplane wings,an energy method based on one-way fluid structure coupling is proposed.To consider the effect of wing vibration,the flow mesh is updated using a fast dynamic mesh technology proposed by our research group.Then the pressure is computed by solving the Reynolds averaged Navier Stokes equations in the arbitrary Lagrangian Eulerian coordinates through the SIMPLE algorithm using the updated flow mesh. The aerodynamic force applied on the wing is calculated using the pressure on the wing surface and then the aerodynamic work is obtained.The aerodynamic damping is assumed to be equivalent viscous damping.Thus the aerodynamic damping can be computed using the calculation formula of equivalent viscous damping,and the flutter boundary is predicted using the aerodynamic damping.The aerodynamic damping of the wing 445.6is computed and the dimensionless flutter velocity of the wing 445.6can be predicted using the proposed energy method.The relative deviation between the dimensionless flutter velocity and the experimental data is about 1.5%.It is found that the aerodynamic damping increases with the order of mode in transonic flows.The distribution of the aerodynamic work on the wing surface shows that the positive aerodynamicwork is mainly caused by the shock wave in the transonic flows.Thus it can be concluded that the transonic flutter of the wing 445.6is mainly induced by the shock wave.