LES study on flow features of the supersonic mixing layer affected by shock waves

The supersonic mixing layer in a model scramjet has been simulated using large eddy simulation (LES) with the consideration of complex shock waves. A comparison with experimental data demonstrates the accuracy and applicability of the employed numerical models and computational methods based on the OpenFOAM solver. The flow features are examined not only from the visualization of flow field, but also from a fundamental point of fluid motion with a focus on evaluating the impacts of shock waves on the turbulent mixing layer. Four basic types of interaction between the shock waves and the mixing layer are discussed according to the flow features and the field development. The mixing properties are analyzed from the evolution of the mixing layer thickness with emphasis on mixing efficiency and total pressure recovery. Results show that three typical developing regions can be observed for the supersonic mixing layer in the scramjet. Shock waves make contributions to the fuel-air mixing due to the amplification of turbulence and the gain of vorticity. The increase in total pressure losses is unavoidable despite the increased mixing efficiency in the presence of shock waves. Additionally, a significant decrease of the convective Mach number is caused by the expansion-fan/shock-wave pattern at the injector exit, leading to a reduction in compressibility effects, which is an important aspect of the physics for the development of the mixing layer in the model scramjet.