Characterization of Lip Thickness Effects in Subsonic Coaxial Jets with Varying Velocity Ratio

This study aims to investigate the influence of lip thickness and velocity ratio on the mixing characteristics of coaxial jets. The primary objective is to examine and compare the flow behavior of thin and thick lip coaxial nozzles at various velocity ratios, using both experimental and numerical methods. The scope of the work focuses on identifying critical lip thicknesses ranging from 0.7 mm to 10.7 mm, in increments of 2 mm. The primary jet exit Mach number is maintained at 0.6, while the secondary jet Mach number is varied from 0% to 100% of the primary jet velocity. Numerical simulations are performed using a validated turbulence model to understand the flow physics, such as potential core variation and jet interaction mechanisms. In this research, the Reynolds number vary from 0 to 1.62x105 and the turbulence intensity has a minimum value for a 4 and it reaches to 4.9 at maximum. The results show that in thin lip nozzles, the increase in velocity ratio extends the potential core length due to dominant shear layer interaction. In contrast, thick lip nozzles display reduced core length with increasing velocity ratio, primarily due to wake region interaction. Among the cases studied, the 10.7 mm lip thickness configuration exhibits superior mixing characteristics, indicating the presence of a critical lip geometry for enhanced performance. These findings provide insight into optimizing coaxial jet design for applications requiring efficient mixing.