Near-field flow of supersonic swirling jets

The addition of swirl to scramjet fuel jets has been proposed as a method of enhancing fuel mixing, but little of a fundamental nature is known about supersonic swirling flows. Several jets with different amounts of swirl were created by tangential injection and acceleration through a convergent-divergent nozzle. The flowfields near the nozzle exit were investigated using pitot, cone, and total-temperature probes, and Rayleigh scattering from a laser light sheet. The results show that tangential injection is an efficient method for generating swirling jets, that the swirling jets mix much more rapidly with the stagnant air than comparable straight jets, and that, when overexpanded, turbulence is created in the jet core as a result of vortex breakdown. Mixing layer growth rates are shown to correlate with Richardson number