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传统的直接模拟Monte Carlo(DSMC)程序以直角网格为基础,在计算复杂的流动边界时不可避免地会带来一定误差。非结构网格虽然能够贴体地适应任何复杂流动边界,但因其拓扑结构的无序性、算法复杂、效率低等缺点而较少使用。该文提出一种基于Delaunay三角形网格的粒子轨迹追踪算法。该算法用背景网格将计算域分成若干矩形区域,通过首先确定矩形区域再搜索三角形网格的方法实现粒子轨迹的追踪与定位。以该算法为核心编制了C语言版本的2维DSMC计算程序。通过与经典文献算例对比,验证了该算法的有效性。利用该DSMC程序研究了真空腔室内喷淋头(showerhead)微孔孔径变化对流场分布均匀性的影响。中性参考气体为氩气,固定入口压力200Pa、温度300K。结果表明:增加微孔孔径有利于提高径向速度和温度分布的均匀性,而减小微孔孔径有利于提高径向压力分布的均匀性。
The traditional direct simulation Monte Carlo (DSMC) program, based on a rectangular grid, inevitably introduces some error in the calculation of complex flow boundaries. Although unstructured grid can fit any complex flow boundary, it is seldom used because of its chaotic topology, complex algorithm and low efficiency. This paper presents a particle trajectory tracking algorithm based on Delaunay triangulation. The algorithm divides the computational domain into a number of rectangular regions by the background grid, and tracks and locates the particle trajectory by first determining the rectangular region and then searching the triangular meshes. Based on this algorithm, C language version of 2-D DSMC calculation program was compiled. The validity of the algorithm is verified by comparison with the classic example. The DSMC program was used to study the influence of the pore size of the showerhead on the uniformity of the flow field distribution in the vacuum chamber. Neutral reference gas is argon, fixed inlet pressure 200Pa, temperature 300K. The results show that increasing the micropore diameter is beneficial to improve the uniformity of radial velocity and temperature distribution, while reducing the micropore diameter is beneficial to improve the uniformity of radial pressure distribution.