关键词: 尾空泡;水下点火;燃气射流;动网格;发射平台

Abstract: When a submarine launched missile is ejected from the launch tube with a gas-steam ejection system, the tail will be attched with gas bubble, the development state of the tail cavitation will affect the establishment of the underwater ignition gas jet flow field. In order to figure out the mechanism about the structure of underwater launching flow field in different working conditions, mixture model and dynamic mesh method are adopted to simulate the dynamic flow field of gas jet under the three wrapping states of the engine in the tail cavity, which included expansion stage, early contraction stage, complete closure, and the corresponding ignition positions are 2.2m, 4.3m, 6.5m, respectively. The simulated results show that the greater the degree of tail cavity shrinkage, the more complicated the flow field structure in the engine nozzle is, the expansion and necking of the tail cavity make the launching platform suffer greater pressure pulsation. When the tail cavity is not in the contraction stage and the engine is ignited at a certain safe distance (4.3m)，it is beneficial to the establishment of the gas jet flow field, and the pressure fluctuation on the launch platform is the smallest, thus it effectively improves the safety of underwater ignition and launching.

Key words: Tail cavity;Underwater ignition;Gas jet;Dynamic mesh;Launch platform