During the parallel separation process of two stages to orbit (TSTO) vehicles, there are multiple reflections of shock waves between the first and second stage vehicles. The complex flow has a great impact on the pressure distribution, torque characteristics and flight attitude of the vehicles, and may even seriously affect the safety of the separation between stages of the vehicles. The parallel separation properties of the two stages to orbit vehicle model created by the National Numerical Wind Tunnel Project are examined using adaptation techniques for unstructured hybrid mesh and the self-developed National Numerical Wind Tunnel Project software, NNW-FlowStar. The simulation results are compared with the wind tunnel test data, and the reliability and effectiveness of NNW-FlowStar simulation of parallel separation characteristics of vehicles are confirmed. The research shows that the NNW-FlowStar can better simulate the parallel separation characteristics of the two stages to orbit the vehicle. The numerical simulation results are in good agreement with the test results. The calculated flow field structure is consistent with the wind tunnel test. Using the mesh adaptive technology can effectively improve the simulation accuracy. T In order to circle the vehicle, the two stages will separate in parallel and travel through several typical flow stages, including combination flow, gap flow, small channel flow, big channel flow, and free flow. During the whole process, the shock structures change rapidly, and there are complex flow phenomena such as shock wave interference, boundary layer interference and shock wave/boundary layer interference.

As an active flow control technology, the opposing jet has become a research hotspot due to its broad prospect in reducing aerodynamic heat. In order to explore the heat flux reduction law and related mechanism of opposing jet flow control for hypersonic vehicles, a hemispherical bluff body model was studied by numerical simulations and wind tunnel experiments under different freestream and opposing jet conditions. The flow field and Stanton number distribution on the model surface were obtained, and both numerical and experimental data were verified against each other. The results suggest that, the heat flux reduction effect of the opposing jet is the consequence of a combined action of the jet backflow and the jet pushing away the front shockwave from the head. At a fixed Mach number, the heat flux reduction effect of opposing jet becomes more obvious with the increase of the jet pressure ratio; while under the condition of a similar jet pressure ratio, better heat flux reduction effect by the opposing jet can be achieved at higher Mach numbers.