Numerical Simulation of Spatial Turbulent Mixing of Supersonic Forced Jets in Coflow

Large-eddy simulations (LESs) were carried out for a symmetry-cell representation of parallel underexpanded Mach 3 jets injected into a Mach 5 supersonic coflow. The objective was to determine how deterministic inlet forcing affects flow field development, coherent flow structures, total velocity fluctuations, and transverse momentum transport. The three-dimensional filtered Navier–Stokes equations were solved via a third-order Essentially Non-Oscillatory (ENO) scheme, while unresolved turbulent scales were represented using the Smagorinsky model. The calculations covered several pressure ratios and forcing frequencies in order to compare the response of the jet under different conditions. The effects of forcing were assessed from the evolution of coherent vortices, Reynolds stresses, and vorticity thickness. The simulations show that the imposed excitation changes the formation and downstream evolution of large-scale structures in the shear layer. Under deterministic forcing, vortex roll-up and pairing occur closer to the jet inlet, accompanied by increases in the total fluctuation stresses and vorticity thickness. A stronger response is obtained at a lower forcing frequency farther downstream. Within the considered symmetry-cell configuration, the results indicate that appropriately selected deterministic forcing can accelerate flow field development and enhance transverse momentum transport.