The effect of density gradient on a confined transverse slot jet
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Jet in cross flow consists of a jet exhausting into a freestream. This flow field has a wide variety of engineering applications including injection in gas turbine engines, flame stabilization in ramjet engines and thrust vector control for maneuvering high speed jet aircrafts. The current study explored the effect of a non-unity density ratio between freestream and the jet, on characteristics of an induced recirculation zone and the flow field in general, resulting from a transverse slot jet issuing into a confined crossflow. The slot jet spanned the entire channel spanwise dimension, which resulted in a quasi two-dimensional flow field. Experimental studies were conducted at various jet to freestream momentum ratios, with a constant freestream velocity and two different density ratios. The influence of non-unity density ratio between jet and the crossflow on static pressure measurements along the wall was demonstrated. Particle image velocimetry results indicated that the jet penetration into the crossflow and the length scales of the recirculation bubble were lower for the case with lower density ratio when the momentum ratio was maintained constant. However, the freestream acceleration, turbulence quantities and vorticity generated were found to be higher for the case with lower density ratio. Finally, high speed schlieren was used to show the evolution of turbulent structures for the cases with a non-unity density ratio.