An Unsteady Momentum Source Method and Its Application in Simulation of Hovering Rotor

一种非定常动量源法及在旋翼悬停模拟中的应用

School of Aeronautics, Northwestern Polytechnical University, Xi'an 710072, China

Received: 12 June 2019

Abstract

The efficiency and accuracy of numerical simulation on power unit is the key to study the relevant aerodynamic layout with multiple rotating power units. However, the numerical simulation of the power unit using real geometry all faces the problem of low solution efficiency. Taking the rotor hovering state as an example, the real blade was firstly simplified and replaced by a thin mesh disk to establish the effective momentum source method. Then, using fan-shaped mesh region that changes with time to replace real blade and simulate the rotation, the unsteady momentum source method which could get the revolution of tip vortex was proposed. The results show that the momentum source method with the input of accurate blade force distribution can simulate rotor wake better, and the influence that blade geometry acts on wake mainly reflects in the blade force distribution. In addition, the unsteady momentum source method can simulate the revolution of tip vortex, and its consumptions of computing resources and calculation time are only about 1/8 of the unsteady numerical simulation based on the real geometry.

摘要

对于含有多个旋转动力单元的流场的求解，其模拟的高效与准确性是研究相关气动布局的关键。而采用动力单元真实模型进行数值模拟的方法，均面临求解效率不高的问题。因此，以旋翼悬停状态为例，首先以薄体网格圆盘代替真实桨叶，建立了高效求解的定常动量源法。接着，在定常动量源法基础上采用扇形网格区域代替真实桨叶，并以该网格区域随时间的变化模拟桨叶旋转，建立了能够模拟桨尖涡生成和发展的非定常动量源法。结果表明，以准确桨叶力分布作为输入的动量源法能够得到较为准确的旋翼尾流，验证了桨叶几何模型对尾流的影响主要体现在桨叶力分布之上；而所建非定常动量源法对桨尖涡的模拟取得了较好的结果，且计算网格量及计算时间只有真实模型非定常模拟的1/8左右，具有更高的求解效率。