Trailing Edge Modifications for Enhanced Jet Decay: The Effect of Groove Depth on Supersonic Rectangular Nozzles

The effect of trailing-edge grooves on the mixing characteristics of rectangular supersonic nozzles with an aspect ratio 2 : 1 is investigated. Both experimental measurements and computational fluid dynamics (CFD) simulations were conducted to analyse the groove depths of 2.5, 5, and 10 mm along the minor axis, as compared with a plain baseline nozzle. The results demonstrate that groove-induced vortical structures significantly enhance shear-layer instabilities and promote ambient entrainment. Among the tested configurations, the 5 mm groove shortens the potential core length by up to 16% for the nozzle pressure ratios (NPRs) of 3–7, achieving the most efficient mixing. The 2.5 and 10 mm grooves yield only marginal improvements, indicating the importance of geometric tuning. These findings confirm that the optimized trailing-edge grooves provide a robust passive flow-control mechanism for high-speed jets, offering potential benefits in propulsion efficiency, jet noise suppression, and infrared signature reduction.