超声速喷管扩张型面对水下喷气推进振荡特性的影响

The effect of the divergent section contour of supersonic nozzle on the multiphase flow and propulsion performance of underwater rocket propulsion nozzle is studied by a series of numerical simulations. The underwater flow processes of conical and parabolic nozzles with different divergent section contours under still water,variable depth and over-expanded conditions are simulated. A numerical model of underwater supersonic gas jet is established based on the volume of fluid(VOF)multiphase model. The influence laws of the contour types and key parameters of divergent section on the nozzle near-field flow structure,flow separation characteristics,and thrust oscillation characteristics are analyzed. The results show that the separation shock structure in the nozzle operating in deep water is highly unstable. The gas-liquid separation may also occur at the separation point in the divergent section,and the nozzle thrust oscillates on the basis of the full-flow value. There is a dynamic transition of flow separation patterns in parabolic nozzles,and the gas-liquid separation phenomenon is not significant under the restricted shock separation(RSS) pattern. The effect of contour type is more pronounced than that of contour parameters, with the parabolic nozzles having more moderate thrust oscillations than the conical nozzles, and the difference is more significant at greater water depths. At a depth of 90 m, the maximum difference in average thrust of the nozzles with different contours reaches 10. 13% of that of the basic parabolic nozzle.