稀薄流航天器鼻锥迎风凹腔气动力和气动热性能研究

To investigate the thermal protection characteristics of forward-facing cavity in rarefied flow, a numerical study in aerodynamic and aerothermodynamics performance on the space vehicle applying the forward-facing cavity in rarefied flow was conducted via Direct Simulation Monte Carlo (DSMC) method. Heat flux distributions along the nose outer wall surface, cavity side wall surface and cavity base wall surface were obtained, afterwards, the thermal-cooling effect and the gas conditions in the forward-facing cavity with different length-depth ratios were analyzed. Moreover, on the basis of the model with length-depth ratios of 1, the variation in the aerodynamic and aerothermodynamics performance with nose lip bluntness radius was quantified to study the effect. The results show that the outer wall surface bears approximately 7% lower heat flux by creating a forward-facing cavity. When the length-depth ratio reaches 1, the trend of heat flux distributions along the cavity side wall surface is very similar, and the axial position where the heat flux drops to the lowest point no longer changes, meanwhile the heat flux along the cavity base wall surface is very small, which is only 28.66% of the model with length-depth ratios of 0.5. The gas near the bottom of the cavity changes from rarefied flow to continuous flow and the gas pressure oscillates. In conclusion, there would be no apparent advantages of heat reduction due to the great increment of drag coefficient employing cavity lip bluntness. Although it can reduce peak heat flux, it would result in more severe aerodynamic degradation.