钝头体高超声速绕流底部失稳特征数值模拟

利用数值模拟方法对高超声速钝锥及Apollo返回舱底部尾迹流场进行了研究, 分析尾迹流动的失稳过程. 对钝锥模型, 在M_∞=6, Re=1.71× 10⁶(Re以球头半径为参考长度)条件下观察到了底部流动的不稳定性. 不添加任何扰动, 数值模拟首先得到的流动是稳定解, 在底部发展出一个主分离区和一个二次分离区, 流动是轴对称状态. 继续进行计算, 发现二次分离线率先变形, 底部流场发展出非定常周期流动. 对Apollo返回舱模型, 在相同条件下 (Re以前面圆弧半径为参考长度), 数值模拟首先得到的流动同样是稳定解, 出现以二次分离线率先变形为起始的结构失稳, 演化出周期性过程, 但持续时间较短, 很快出现了非周期非对称状态. 研究表明, 高超声速钝锥及Apollo返回舱底部流场均存在不稳定性问题, Apollo返回舱的底部流场更加不稳定.

NUMERICAL STUDY OF THE STABILITY OF HYPERSONIC BASE FLOW OVER A BLUNT BODY AND APOLLO COMMAND MODULE

The structural instabilities of base flow are presented by using numerical simulation in this paper in hypersonic base flow over blunt cone with M_∞=6,Re=1.71×10~6(based on the nose radius) and Apollo command module with M_∞=6,Re=1.71×10~6(based on the nose radius).Stable solutions are first obtained to show a primary separation and a secondary separation zone in flow over blunt body at M_∞=6.Later, without any arbitrary disturbance imposed,the structural instability still occurs after a certain critical time. The evolving process of the structure of flow over blunt body is a periodic behavior in the forepart,but there is non-periodic behavior observed at M_∞=6 in spite of long calculation time.For Apollo command module,the simulation result is similar to that of the blunt body,while the base flow of Apollo command is more instability than that of blunt cone.This research indicates that the present numerical simulation method can be used for the study of the stability of base flow.