ARTICLES YOU MAY BE INTERESTED INHigh-enthalpy models for boundary-layer stability and transition Physics of Fluids 31, 044101 (2019); https://doi.org/10.1063/1.5084235Numerical study of the shear-thinning effect on the interaction between a normal shock wave and a cylindrical liquid column Physics of Fluids 31, 043101 (2019); https://doi. ABSTRACTFilm cooling is generally considered as a promising active cooling technology for developing thermal protection systems of hypersonic vehicles; however, most of experimental and numerical studies of film cooling mainly concentrated on gaseous film cooling. Since the phase change of liquid coolants can absorb a large amount of latent heat, liquid film cooling should have more potential advantages, especially for severe environments accompanied by hypersonic flight. To address this issue, the film cooling using water as a coolant was experimentally investigated in hypersonic flow. Experiments were carried out in a detonation tunnel, at a hypersonic Mach number of 6 using a 25 ○ apex-angle wedge. Characteristic physical quantities, such as surface temperature rise, shock wave structure, film thickness, and cover area, are measured by thermocouples, schlieren, and a specially devised liquid film measurement system. The experimental results verify that the liquid film cooling is feasible in hypersonic flow and also indicate that it is featured with maintaining aerodynamic performances due to the weak effect on the main flow caused by coolant injection. Inspired by these results, liquid film flow characteristics and its influencing factors including mass flow rate, dynamic pressure, coolant injection direction, and surface tension are investigated to guide the design of a thermal protection system. Published under license by AIP Publishing. https://doi.Published under license by AIP Publishing FIG. 15. Effects of the coolant injection direction on the liquid film thickness and coverage area width. (a) θ = 0 ○ , (b) θ = 30 ○ , (c) θ = 60 ○ , and (d) cover area width.

The flow near the stagnation streamline of a blunt body is often attracted and analyzed by using the approximation of local similarity, which reduces the equations of motion to a system of ordinary differential equations. To efficiently calculate the stagnation-streamline parameters in hypersonic magnetohydrodynamic (MHD) flows, an improved quasi-one-dimensional model for MHD flows is developed in the present paper. The Lorentz force is firstly incorporated into the original dimensionally reduced Navier-Stokes equations to compensate for its effect. Detailed comparisons about the shock standoff distance and the stagnation point heat flux are conducted with the two-dimensional Navier-Stokes calculations for flows around the Orbital Reentry Experiment (OREX) model, including gas flows in thermochemical nonequilibrium under different magnetic field strengths. Results show that the shock curvature should be considered in the quasi-one-dimensional model to prevent accuracy reduction due to the deviation from the local similarity assumption, particularly for hypersonic MHD flows, where the shock standoff distance will increase with larger magnetic strength. Then, the shock curvature parameter is introduced to compensate for the shock curvature effect. A good agreement between the improved quasi-one-dimensional and the two-dimensional full-field simulations is achieved, indicating that the proposed model enables an efficient and reliable evaluation of stagnation-streamline quantities under hypersonic MHD flows.