Numerical and Experimental Study of Tandem Dual Jet Injection into a Supersonic Cross Flow

To minimize the length of supersonic-combustion ramjets (scramjets) required for the injected fuel to mix rapidly with the supersonic cross flow, tandem dual jet injection shows improved mixing performance over single jet injection. The present study comprises experimental work of tandem dual jet injection, using Schlieren flow visualization in a supersonic wind tunnel, as well as numerical simulation of this flow inside the wind tunnel channel, both at Mach 1.6 inflow. The numerical simulations are based on (a) the Reynolds-averaged Navier-Stokes (RaNS) equations for the time-averaged flow, and (b) the time-resolved Delayed Detached Eddy Simulation (DDES). From the wind tunnel Schlieren images, the time-averaged location in the cross flow of the upper boundary of the main jet plume is found to obey an empirical similarity relation, providing for a given jet-to-cross-flow momentum flux ratio J the value of the dimensionless distance S between the jets for which plume penetration into the cross flow is maximal. Numerical simulations facilitated detailed analysis of the time-dependent flow and were used to obtain insight in the flow phenomena that occur in the interaction of the jet plume with the supersonic cross flow, and to validate the experimentally obtained empirical similarity relation.