基于两级直角网格结构的三维DSMC算法研究

An algorithm study of three-dimensional DSMC simulation based on two-level Cartesian coordinates grid structure

结合直角网格计算的高效率以及表面非结构网格对飞行器几何外形的精细描述,本文建立了基于两级直角坐标网格结构的DSMC数值模拟算法。一级网格为计算区域离散后的背景网格,二级网格为独立的碰撞网格和取样网格,是在背景网格的基础上根据流场性质的变化经过自适应后获得的亚网格,碰撞分子对在亚网格内选取,以保证选取的分子是"最相邻的"。计算的Orion飞船外形从自由分子流到稀薄过渡流的气动力系数,与DS3V和DAC软件计算结果的一致性非常好,验证了本文算法的可靠性和有效性。同时对过渡区的流动特征和表面气动参数的分布规律进行了分析。

Combining Cartesian grids of high computational efficiency with precise description of unstructured triangular cells on vehicle geometry surfaces,the DSMC numerical simulation method based on two-level Cartesian coordinates meshes is presented in this paper.Level-I grids which referred as background cells created by uniform Cartesian grids in computational regions.Level-II grids are separate collision and sampling cells which are the division of background cells into sub-cells during the adaptation procedure according to the local flow gradients.The molecular collision pairs are selected in sub-cells to produce nearest neighbor collisions.The calculated aerodynamic coefficients of Orion configuration from free molecular flow to transitional flow have good agreements with DS3V and DAC codes.The reliability and validity of current technical scheme and its code are verified by the comparisons.The computational results of flow field and surface aerodynamic parameters are also analyzed and they have better regularity.