中文摘要：

采用耦合求解轴对称非定常NS方程与一维分离动力学方程的方法，对多级火箭低空级间热分离初期过程进行数值仿真。依据仿真结果描述低空级间热分离初期流场的两种典型结构：内部为喷管扩张段流动分离以及外部为级间缝隙横向喷流与超声速外流的干扰流场；给出两种典型流场结构中位于上面级弹体表面（喷管内）的流动分离点位置以及壁面压力分布随仿真时间的变化；初步估算流动分离线偏斜时内外流动分离区域对上面级弹体的十扰力矩。通过分析数值模拟与力矩估算结果，发现在低空级间热分离内外流场中流动分离激波后方形成的高压区域是上面级所受干扰力矩的重要来源。研究结论可为级间热分离过程干扰机理研究提供理论方向，为级间热分离时序设计提供参考。

英文摘要：

Based on the method of the unsteady axisymmetric NS equation coupled with one dimension separation dynamics equation, the initial phase of multi-stage rocket stage separation is numerical simulated. According to the simulation result, the two typical flow structures of initial phase of stage separation at low altitude are described： nozzle divergence dection flow separation inside the inter-stage area, interactive flow field of lateral jet flow impacting on the upstream incoming flow outside the inter-stage area. Time histories of flow separation position located on the upper stage （ or in the nozzle） and wall pressure distribution are presented. The disturbance torques due to the tilted flow separation lines of both inside and outside flow are preliminarily estimated. The research firstly discovered that high pressure zone behind the flow separation shock of both inside and outside flow are the important sources of the disturbance imposed on the upper- stage by the staging action. The results can provide a direction for the research of stage separation disturbance mechanism and a reference for timing sequence design of stage separation.