Numerical investigation of vented plume into a supersonic flow in the early stage of rocket hot separation

In the early stage of rocket hot separation, the vented plume from separation gap interacts with the supersonic incoming flow, causing lateral interference which affects separation safety and flight stability. In this work, steady interstage interference flow fields of a two-stage rocket in different incoming flow conditions (Mach number from 2.5 to 5.5, angle of attack from 0° to 6°, flight altitude from 16 Km to 24 Km) are numerically studied by the compressible Reynolds Averaged Navier-Stokes equations with SST turbulence model. An annular lateral jet is used to simulate the vented plume near the separation gap. Firstly, the interference flow fields with and without angle of attack are analyzed in detail to illustrate the interference mechanism of lateral jet. Then, the effects of flight altitude, jet total pressure, separation distance and free-stream Mach number on lateral jet interaction are investigated. With the increase of flight altitude, jet total pressure and separation distance, the upstream separation length and the pressure peak increase, and the peak position moves upstream. Nevertheless, with the increase of free-stream Mach number, the upstream separation length is shortened, the pressure peak raises and the peak position shifts to the downstream. Besides, a combined parameter named momentum ratio is introduced to involve various factors, and the upstream separation length increases linearly with the momentum ratio when the momentum ratio is between 0.03 and 0.173. Finally, the influences of angle of attack on the disturbing force and moment of the upper stage are discussed. Numerical results indicate that the direction of the disturbing force is downward and the magnitude first rises and then falls with the angle of attack. The disturbing moment makes the upper stage have a tendency of subduction and increases with the angle of attack.