Investigation of Rotor Tip Vortex in Hover Based on IDDES Methods

悬停状态旋翼桨尖涡IDDES方法数值模拟研究

¹ AVIC Jiangxi Hongdu Aviation Industry Group, Nanchang 330024, China
² School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China

Received: 6 March 2018

Abstract

A calculation and analysis program of high-precision numerical simulation for rotor blade tip vortex in hovering state was developed. The fifth order Roe-WENO scheme was carried out in order to reduce the numerical dissipation of the rotor wake region. The rotary motion of the rotor was realized by using the dynamic patched technology of structured grids. And at the same time, the technology also helped to avoid the tremendous increase of grid number of the far-field due to the refined grids of the flow region where emphasis was placed on. Hybrid RANS/LES approach was investigated based on the issues about inadequate capabilities of simulations of complex turbulent flows, and IDDES approach was developed. The numerical simulation of the tandem cylinder was carried out firstly to verify the reliability of the IDDES method and the patched grid technology. Then the RANS and IDDES approaches were used to simulate the flow field of the rotor in hover performance, respectively. The analysis of the vortex magnitude, vortex core position and diameter as well as the velocity profiles of the rotor tip vortex were made comparatively in detail. The numerical results showed that the resolutions obtained through IDDEES approach agreed with the experimental results much better than that of the RANS approach with the same gird scales. Meanwhile, the IDDES results can capture the tiny worm vortex structures and vortex paring phenomena in accordance with the practical status, which contributes to study the flow mechanism of rotor and related problems.

摘要

开发了一套适用于悬停状态旋翼桨尖涡高精度数值模拟研究的计算分析程序。采用五阶Roe-WENO格式来降低旋翼尾迹区域内的数值耗散。采用结构网格动态面搭接技术实现旋翼的旋转运动，同时该技术还解决了对流动关注区域进行网格加密引起远场网格数量剧增的问题。针对RANS方法对复杂湍流流动模拟能力不足的问题，对RANS/LES混合方法进行了研究，开发了基于IDDES方法的计算程序。首先以串列双圆柱绕流问题为算例，验证了所采用的IDDES方法和面搭接技术的可靠性。然后分别采用RANS方法和IDDES方法针对旋翼悬停状态流场进行了数值模拟对比分析，从旋翼桨尖涡的涡强度、涡核位置、涡核直径以及桨尖涡涡核附近气流速度型分布等方面对旋翼桨尖涡结构的细节特征进行了比较系统的分析。计算结果表明，在相同的网格分布下，IDDES方法计算得到的结果较RANS方法更为接近实验结果，同时IDDES的计算结果还捕捉到了与实际情况相符的细小蠕虫涡结构与桨尖涡的"涡对"等细节现象，有利于深入研究旋翼绕流机理及相关问题。