Numerical studies have been performed to visualize vortical flow structures emerged from jet cross-flow interactions. A single square jet issuing perpendicularly into a cross-flow was simulated first, followed by two additional scenarios, that is, inclined square jet at angles of 30° and 60° and round and elliptic jets at an angle of 90°, respectively. The simulation considers a jet to cross-flow velocity ratio of 2.5 and a Reynolds number of 225, based on the free-stream flow quantities and the jet exit width in case of square jet or minor axis length in case of elliptic jet. For the single square jet, the vortical flow structures simulated are in good qualitative agreement with the findings by other researchers. Further analysis reveals that the jet penetrates deeper into the cross-flow field for the normal jet, and the decrease of the jet inclination angle weakens the cross-flow entrainment in the near-wake region. For both noncircular and circular jet hole shapes, the flow field in the vicinity of the jet exit has been dominated by large-scale dynamic flow structures and it was found that the elliptic jet hole geometry has maximum “lifted-off” effect among three hole configurations studied. This finding is also in good qualitative agreement with existing experimental observations. 1. Introduction The problem of injecting fluid through pipe/duct geometry into a mainstream cross-flow domain presents in many industrial and engineering applications, for example, turbine blade film cooling, fuel injection in IC engine, thrust, and noise control of S/VTOL aircraft, fuel-air mixing in gas turbine combustors, and pollutant dispersion from chimney stacks. Due to these wide range applications, the jet in cross-flow (JICF) configuration has been the subject for numerous experimental and theoretical studies. Since the observation of coherent structures in earlier 1970s, various experiments have been devoted to JICF research (see, e.g., Margason [1]) and it was believed, based on those studies, that the dynamic process of flow motions in the JICF is closely relevant to and, at some extent, predominated by the formation and evolution of large vortical structures, which are originated from the jet shear layer, evolved after the jet exit, and decayed further downstream. Fric and Roshko [2] identified four different vortical structures presented in a JICF system for the first time and pointed out that the counterrotating vortex pair (CRVP) is the dominant vortical structure in this kind of complex flow systems. Despite the fact that the inclined jet and jet with
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