The present study aims to simulate both controlled and uncontrolled Mach 1.86 jets from a convergent–divergent nozzle using computational fluid dynamics (CFD). A rectangular cross-wire with a 5% area-blockage was used as a passive control device at the nozzle exit to enhance jet
mixing. The two-dimensional nozzle model was created in ANSYS Workbench, and the governing equations were solved using the FLUENT solver with the realizable k−ε turbulence model. Simulations were performed for nozzle pressure ratios (NPR) ranging from 4 to 9. The results
show that the jet core length decreases under controlled conditions, confirming enhanced mixing. Pressure variation significantly affected flow development: at moderate NPRs (5–6), the jet was overexpanded and showed a 21–27% core reduction, whereas at a higher NPR (9), stronger
under expansion led to about a 37% reduction due to greater shear-layer instability and more intense vortex formation. Mach number contours are used to examine the presence of shocks in the jet and the wave structure. This study demonstrates the substantial benefits that a simple
cross-wire used as a passive device offers in enhancing mixing in supersonic jets. The outputs of this study will be beneficial in suppressing aerodynamic noise, improving jet combustion, and enhancing propulsion efficiency.