Simulations of Mixing for Normal and Low-Angled Injection into Supersonic Crossflow

摘要

The mixing of fuel injected into a supersonic crossflow is simulated using an approach that combines an unstructured grid framework, fully implicit time integration, low-dissipation flux evaluation scheme, and hybrid Reynolds-averaged Navier-Stokes and large-eddy simulation turbulence modeling. This approach allows for the simulations to resolve the large-scale unsteady structure that plays an important role in the mixing process and that makes this flow difficult to simulate accurately using steady-state simulations. A separate hybrid Reynolds-averaged Navier-Stokes and large-eddy simulation of a flat-plate boundary layer is used to supply an unsteady inflow boundary condition for the simulations. This provides a realistic forcing to the jet plumes, which is needed to predict the correct mixing for some cases. The purpose of the work is to validate this simulation approach to the extent possible, using available experimental measurements. The simulations correspond to a set of mixing measurements made for nonreacting injection of ethylene into a Mach 2 crossflow. Injection occurs through circular injector ports oriented at either 90 or 30 deg with respect to the freestream. For each injection angle, multiple jet-to-freestream momentum flux ratios are simulated. The results of the simulations are qualitatively compared with the mean and standard deviation of planar laser-induced fluorescence intensity image sequences. The simulations are found to accurately reproduce the structure and development of the jet plumes for each of the cases. Results are quantitatively compared with mean ethylene mole-fraction distributions obtained via Raman scattering. The simulation results compare very well to the experimental data, although the jet plume penetration and mean injectant concentration levels were overpredicted in some regions.