Effect of lip-thickness on rectangular nozzle co-flowing subsonic jet

Abstract The reduction in the potential core length and the enhancement of mixing by varying the lip thickness with co-flowing jets through a rectangular nozzle have been investigated using both computational and experimental methods. The lip thickness of a nozzle is defined as the thickness of the primary nozzle wall that separates the primary and secondary co-flowing jets at the nozzle exit. A baseline rectangular nozzle with a hydraulic diameter of 6 mm and three co-flow nozzles with annular co-flows with lip thicknesses (LT) of 25 %, 50 %, and 75 % of the baseline hydraulic diameter were designed and studied for a subsonic jet Mach number of 0.8.The jet centerline pressure decay, radial total pressure decay, and jet mixing behavior were analyzed. The results show that increasing the lip thickness enhances the mixing characteristics of the primary and secondary flows. The reduction in the potential core length was 39.39 % for the 75 % LT configuration compared with that of the plain convergent rectangular nozzle, and 7.27 % and 19.24 % for the 25 % and 50 % LT configurations, respectively.