Topology Structure Stability and Global Stability Analysis of Hypersonic Wake Flow over Blunt body

摘要

The flow structural instabilities of base flow in hypersonic wake over blunt body are presented by using numerical simulation in this paper. M∞=6, Re=1.71E+6 (based on the nose radius) are calculated for sphere, blunt cone and Apollo command module. Stable solutions are obtained and there are a primary separation and a secondary separation zone in flow over sphere 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 sphere is a periodic behavior in the forepart, but there is non-periodic behavior observed at M∞=6 in spite of long calculation time. For blunt cone, the simulation result is similar to that of a sphere. For Apollo command module, the evolving process of the flow structure is a periodic behavior in the forepart, but it evolves into a non-periodic behavior after a critical time. In the case of sphere, the results by global stability theory, topology structure analysis and results of power spectrum are compared each other. The global stability analysis method can give a good prediction result. This study result indicates that the present numerical simulation method, topology structure and global stability analysis method can be used for the study of the stability of base flow and confirms that hypersonic flow at the base is also instability.