三维非结构网格DSMC方法的实现及其应用

研究了三维非结构网格DSMC方法实现的过程。将Bird位置元方案中的子网格思想引入到非结构网格上来,只存储子网格的总体标识号,利用较少的计算网格提高了分子的分辨率与计算精度。提出了将体积元坐标搜索算法与交替数字二叉树搜索算法(ADT)相结合的方法来跟踪模拟分子在网格之间的迁移,使用ADT方法判别分子与物面是否作用,避免了分子表面反射的非确定论判据。利用Fortran 90的动态分配内存技术编制了通用计算程序。最后对高超声速过渡流域航天飞机头部外形绕流进行了数值模拟,数值结果初步验证了算法的可行性。

Implementation of 3D unstructured DSMC method and its application

In this paper,the implementation of three-dimensional unstructured DSMC method is studied to calculate hypersonic rarefied flow.The idea of sub-cell of Bird's Position Element Method is introduced into the three-dimensional unstructured DSMC method,by which only ID number of sub-cell is stored.An automatic searching method is presented to improve computation efficiency and save computation time,which is a coupling of volume coordinate searching algorithm and alternative digital tree(ADT) searching algorithm.As a consequence,not only is the computation time reduced,but also is the computation precision largely improved.The deterministic criterion for a molecule to reflect on a certain surface element is used by ADT algorithm instead of a probabilistic one.Dynamic allocation feature of Fortran90 is fully exploited,which makes the code more flexible.Finally,a numerical experiment is made to directly simulate hypersonic rarefied gas flow of the transition regime past nose of space shuttle.In some extent,the results of numerical experiment confirm the feasibility of method mentioned above.