Experimental and numerical studies of co-flowing jets with finite lip thickness and varying bypass ratio.

The study aims the effect of finite lip thickness and bypass ratio on subsonic and correctly expanded sonic co-flowing jet. The co-flowing jets characteristics were studied for two different lip thicknesses at subsonic Mach 0.6, 0.8, and sonic Mach 1.0 by varying the bypass ratio also the co-flowing jet area. The lip thickness considered for the study case is 1.0D_p and 1.5D_p (D_p – primary nozzle diameter is 10 mm). For experimental setup, the co-flowing duct area was varied the secondary inlet with 4 mm and 5 mm holes. Axial Pitot static tube survey was conducted experimentally. The numerical simulations were also carried by commercial code FLUENT- 6.3.2 for solving the RANS equations using Spalart–Allmaras turbulence model. The flow field has been visualised using numerical contours. The results indicate that for lip thickness 1.0D_p and for low bypass ratio, potential core seems to be thicker. Similar behaviour is observed in 1.5D_p lip thickness. On the other side, for both the lip thickness, 1.0D_p and1.5D_p, as the bypass ratio increases a recirculation zone occurs in the near field region and it becomes dominant. For bypass ratio 6.4 and 1.0D_p lip thickness, the recirculation zone exhibits an outer and an inner vortex. [ABSTRACT FROM AUTHOR]