Numerical investigation on the effect of flight and tunnel conditions on the interference structures of Ma7 hypersonic inlet

Abstract

Due to the limitations of size and low enthalpy of the general ground facilities, there are deviations between the flow structures and performance validated by ground tunnel experiments of a scaled inlet model and that of a full-scale model under practical flight conditions. To closely combine the results of ground and flight experiments and speed up the design of hypersonic vehicles, it’s important to investigate the influence of the test environment on the performance of the hypersonic inlet. The present study is motivated to elucidate the influence of incoming environment on the interference flow characteristics of a hypersonic inlet. Numerical simulations are conducted to investigate the effect of difference of flight and tunnel conditions on the performance of Ma7 inlet. The k-ω SST model is used for modeling turbulence and a turbulence model study is conducted to validate its ability. A grid sensitivity study is performed to examine the validity of simulation results. Details of flow characteristics of shock/shock interference (SSI) near the cowl lip and shock-wave/boundary-layer interference (SWBLI) in the isolator are compared and analyzed under the two conditions. The results indicate that SSI configurations near the cowl lip change greatly in different incoming environments. The flow structures at the lip directly determine the location and intensity of SWBLI downstream in the isolator. Compared with flight condition, the boundary layer separates earlier and the separation bubble extents larger under tunnel condition. Different flow characteristics lead to different distribution laws of surface aerodynamic parameters, and there does not exist simple conversion relationship. The nondimensionalized pressure and heat flux on the cowl lip are higher under the tunnel condition than those in the flight environment, whereas the surface aerodynamic parameters of the inlet are lower. When the hypersonic inlet operates at off-design point, the subsonic region generated by boundary layer separation moves closer to the cowl lip under the tunnel conditions than that in the flight environment. This indicates that the starting performance of the hypersonic inlet tested in the general tunnels tends to be a conservative estimation.