Characteristics of a co-flowing jet with varying lip thickness and constant bypass ratio

Purpose Subsonic commercial aircraft operate with turbo-fan engines that operate with moderate bypass ratio (BR) co-flowing jets (CFJ). This study aims to analyse CFJ with constant BR 6.3 and varying primary nozzle lip thickness (LT) to find a critical LT in CFJ below which mixing enhances and beyond which mixing inhibits. Design/methodology/approach CFJ were characterized with a constant BR of 6.3 and varying lip thicknesses. A single free jet with a diameter equal to that of a primary nozzle of the co-flowing jet was also studied for comparison. Findings The results show that within a critical limit, the mixing enhanced with an increase in LT. This was signified by a reduction in potential core length (PCL). Beyond this limit, mixing inhibited leading to the elongation of PCL. This limit was controlled by parameters such as LT and magnitude of BR. Practical implications The BR value of CFJ in the present study was 6.3. This lies under the moderate BR value at which subsonic commercial turbofan operates. Hence, it becomes impervious to study its mixing behavior. Originality/value This is the first effort to find the critical value of LT for a constant BR for compressible co-flow jets. The CFJ with moderate BR and varying LT has not been studied in the past. The present study focuses on finding a critical LT below which mixing enhances and above which mixing inhibits.