基于非结构嵌套网格和逆风格式的旋翼悬停流场数值模拟

Numerical simulation on rotor flowfield in hover based on unstructured embedded grid and upwind scheme

为更好地计及桨叶间相互影响,同时捕捉桨尖附近的流场细节,发展了一套非结构运动嵌套网格方法,并针对关键的贡献单元搜寻问题提出了一种高效的搜索方法。为了可方便地扩展到前飞状态的计算,同时为提高旋翼流场涡量的捕捉精度和效率,采用双时间法求解惯性坐标系下的非定常N-S主控方程,空间方向上使用二阶迎风格式,在此基础上,将不同精度格式的计算结果与试验值进行对比,并讨论了桨尖形状变化对旋翼气动特性的影响,结果表明本文建立的CFD方法对旋翼悬停流场的模拟是很有效的。

To consider the interactional effects among the blades and capture the details of the flowfield around the blade tip, an unstructured embedded grid technique was developed. Aiming at solving the important donor element searching problem, a high-efficient method was presented also. In order to make the present solver to be suitable for conveniently calculating the flowfield at forward flight condition, and to improve the accuracy and efficiency of capturing rotor vortieity, a dual-time stepping approach was adopted to solve the unsteady N-S equations. At the same time, a second-order upwind scheme was employed to calcu- late the fluxes. Then the calculated results simulated by different schemes precision were compared with the available experimental data, and the effects of blade-tip shape on the rotor aerodynamic characteristics were analyzed, which demonstrated that the present method is effective to calculate the flowfield of the helicopter rotor in hover.