Comparative analysis of dual (wall-offset) and parallel jets: flow dynamics and vortex shedding characteristics

Abstract

In the current investigation, comparison between a flow which combines a wall jet and an offset jet, named dual jets (DJ), and two free parallel jets (PJ) is performed considering the same jet’s spacing to jet width ratio d / w  = 1. The number of Reynolds (Re) calculated based on the jet width w is considered equal to 10,000. Two-dimensional (2D) unsteady RANS equations have been adopted to simulate both the flow configurations. As clearly depicted from the mean flow finding in the current investigation, far away from the nozzle plate ( x  = 0), the two jets in PJ configuration merge into a single free jet, while in DJ configuration, they combine to form a single classical wall jet. For the two configurations, the time-dependent computation results show a periodic vortex shedding (PVS) phenomenon near the ejection plate. This phenomenon is like what would be observed behind the flow over 2D bluff body. The dimensionless Strouhal number (St) representing the frequency of vortex shedding in the case of PJ (St = 0.24) is noted to be higher than that for the DJ (St = 0.22).