直升机旋翼下洗流场的数值模拟

建立了三维欧拉方程数值模拟旋翼流场的方法和模型，以用于实际直升机旋翼诱导速度场计算，为火箭导弹发射提供一个旋翼下洗流场计算方法。在该模型中，使用格心形式有限体积法来求解旋翼流场，时间推进应用五步Runge—Kutta方法，并采用了由动量理论导出的远场边界条件，使用了当地时间步长和隐式残值光顺的加速收敛措施；进行了算例计算，分别给出了Caradonna模型旋翼桨叶表面压力分布以及AH-1G模型旋翼流场中沿导弹发射线上的诱导速度分布的计算结果，与可得到的试验数据进行了对比，吻合良好。最后，得出了几点结论。

Numerical Simulations for the Downwash Flowfield of Helicopter Rotors

A numerical method using the three-dimensional Euler equations is presented to predict the rotor induced velocity flowfield of a real helicopter and to provide a calculated method on the downwash flowfield for rocket or missile emission on helicopters. In this method, a cell-centered finite-volume method and a five-stage Runge-Kutta scheme are employed for the solution of Euler equations, and the far-field boundary condition derived from the rotor momentum theory is used. In addition, the techniques of the local time stepping, implicitresidual smoothing are introduced to increase the convergence rate of the solution. Preliminary simulation results on surface pressure distributions and induced velocity distributions along the rocket trajectories are presented for a two-bladed Caradonna model rotor and AH-1G model rotor in hover at different collective pitch angles respectively. Good agreements are made with measurements. Finally, several conclusions are presented.