直接统计模拟位置元方法中的分子表面反射确定论判据

在直接模拟Ｍｏｎｔｅ－Ｃａｒｌｏ（ＤＳＭＣ）方法的位置元方法中准确判断分子是否与某一表面元相撞，直接关系着气动力热的计算精度，是方法需要解决的关键问题。本文发展的分子表面反射判据，使这个问题得到了有效的解决。此外，还讨论了分子空间位置坐标的记录方法、分子碰撞对的极限距离、网格自适应等实际模拟技术。与圆球自由分子流准确解和过渡领域贴体网格ＤＳＭＣ模拟结果的比较，证明了上述判据和技术的有效性。

A Molecular Reflection Deterministic Criterion Used in the Position Element Algorithm of Direct Statistical Simulation

The present paper suggests a molecular deterministic reflection criterion used in position element algorithm to precisely judge whether a molecule is in collision with surface element. Other problems caused by introducing molecular collisions, such as a method of recording molecular locations, limiting distance of a molecular collision pair, and an automatic adaptive grid generation scheme, are also discussed. Comparison with the exact results for free molecular flow and with the DSMC results based on body fitted grid for transitional flow of a sphere confirms the validity of the suggested criterion and techniques.