用多重网格方法计算旋翼跨声速无粘流场

发展了一种加快悬停旋翼无粘流场计算收敛速度的多重网格方法。由于悬停旋翼流场中存在不可压区域，同时旋翼尾涡系统的发展需要较长的时间，使得旋翼流场的收敛速度远低于固定翼流场，因此研究旋翼流场的多重网格算法具有重要意义。空间离散格式采用了中心有限体积方法，时间推进应用了五步龙格-库塔法。采用3层网格的V循环，对一跨声速悬停旋翼无粘流场进行了数值计算。计算结果表明：尽管多重网格方法对旋翼流场的加速收敛作用不如对固定翼流场的加速收敛效果，但是多重网格方法仍然可以显著地加快旋翼流场收敛。

Euler solutions of transonic flow for a helicopter rotor in hover using multigrid method

An effective multigrid method has been developed to accelerate the Euler solution of transonic flow for a helicopter rotor in hover. The motive of using multigrid method is the following reasons: the flow near the hub is incompressible flow, which can slow the convergence; for the most part, the net flow velocity at the plane of the rotor and in the rotor wake itself is comprised of the velocities induced by the wake especially by the tip vortices. so the full development of wake is very important for the convergence of the flow field, but it require a long time in the numerical simulation. Accordingly, the application of acceleration measure is very useful for the rotor computation. In this Euler solver, we use the cell-centered finite volume method in space and advance the solution in time using five-step Runge-Kutta method. A three-level V cycle multigrid method is implemented in a transonic flow computation. Numerical results show that the multigrid method for rotor flow is less effective than for fixed wings, however it can speed up the rotor flow convergence rate remarkably.