Near Field Decay of Mach 2 Elliptical Jet in the Presence of Tangentially Injected Secondary Swirling Flow

Abstract

This investigation explores the mixing promoting capability of tangentially injected secondary swirling flow on a Mach 2 elliptical jet issuing from an elliptical nozzle of aspect ratio 2. A detailed three-dimensional numerical analysis was carried out for the combination of different levels of pressure gradient at the nozzle exit and five swirl numbers. Reynolds-Averaged Navier-Stokes equation along with Shear Stress Transport model was solved to predict the flow filed. The presence of secondary swirling flow created large pressure gradient in the direction perpendicular to jet axis, resulting in enhanced mass entrainment leading to high spread of the controlled jet compared to the uncontrolled jet. Also, the secondary jet increased the turbulence level in the flow field for all the cases studied compared to that of free jet case, leading to a reduction in jet core length. The swirl number and the pressure gradient at the nozzle exit is found to have a strong effect on the core length reduction. A maximum of about 70% reduction in core length was achieved for nozzle pressure ratio 4 with secondary flow of swirl number 5.