国家数值风洞风雷软件结构/非结构混合网格同构计算特性

Homogeneous Computational Performance of the Structured/Unstructured Hybrid Grid in NNW-PHengLEI

传统计算流体力学(CFD)结构与非结构网格在网格生成难度、近壁区网格质量、远场网格密度等方面均具有互补性,若能够将两者结合构造“结构/非结构混合网格”,便可充分发挥不同网格类型的优势。基于国家数值风洞风雷软件的任意网格“同构混合计算”框架,采用RAE2822翼型和ONERA M6机翼标模算例,以日常生成习惯并保证网格规模相近的情况下,构造了结构、非结构以及结构/非结构混合网格,对比分析了不同类型网格的求解特性。初步研究结果表明,对于跨声速激波弱分离流动问题,采用风雷软件求解结构/非结构混合网格能够得到与实验数据吻合较好的计算结果,同时收敛性和计算效率较纯结构和非结构网格也更好。但结构-非结构计算域交界面处存在变量的不连续,近壁区结构网格的层数会对计算结果产生明显影响,只有保证足够的结构网格覆盖范围以及较好的过渡性才能保证近壁区求解精度。此外,根据计算经验提出了结构/非结构混合网格的生成策略和调用风雷软件进行计算的应用指南,能够为风雷软件工程应用提供参考。

The structured and unstructured grids of traditional CFD are complementary in terms of complex grid generation,near-wall grid quality,and far-field grid density.If they can be combined as“structured/unstructured hybrid grid”,the advantages of different grid types can be fully utilized.Based on the arbitrary grid frameworks for“homogeneous hybrid computation”of NNW-PHengLEI software,the structured,unstructured and structured/unstructured hybrid grids of RAE2822 airfoil and ONERA M6 wing are constructed with daily generation strategy and similar grid size.The computational performance of different grid types are compared and analyzed.For weak shock-induced separated flow,the preliminary results show that structured/unstructured hybrid grid can get better agreement with the experimental data,and the convergence and computational efficiency are better than those of the structured and unstructured grids.However,there is a discontinuity in the variables at the interface between the structured-unstructured domains,and the number of layers of the structured grid in the near-wall region will obviously affect the computational results.Only by ensuring sufficient coverage of the structured grid and better grid transition,the solution accuracy of the near-wall region can be guaranteed.In addition,according to the computational experience,the generation strategy for structured/unstructured hybrid grid and the application guidelines using NNW-PHengLEI have been proposed,which can provide reference for engineering applications.