Numerical simulations of the transverse injection and mixing with a Mach 3 supersonic cross-flow

Numerical simulations of the transverse injection of helium (surrogate for hydrogen) into a Mach 3 cross-flow through circular and wedge injectors have been carried out. Three-dimensional, compressible, steady Favre-averaged Navier-Stokes equations have been solved using the SST k-ω turbulence model. Flow conditions of the injectors are matched to isolate the effect of injector geometry. Mach number contours inside the injector reveal the flow at the exit of the injector to be supersonic and not sonic, as it is usually assumed to be. Oil flow visualisation shows flow features such as a bow shock and separated flow regions around the injectors. Shadowgraphs reveal two parallel shock waves originating from the injection location as well as the thickening of the boundary later downstream of the injector. Helium mass fraction contours on axial planes show the injectant plume and its spreading in the vertical and spanwise (lateral) direction. Performance metrics such as penetration height and degree of mixing of the injectors have been compared. Results show that the circular injector has better mixing performance when compared to the wedge injector for the operating conditions considered. Results from the present calculations show reasonable agreement with experimental data from an earlier study.