On Flow Field of Radially Emitted Underexpanded Jet

Abstract

A radial jet issuing from a slit nozzle is studied experimentally and numerically in this paper. It is a simple model of the wall jet for an axisymmetric jet when it impinges on a flat plate perpendicularly. The slit nozzle is a spacing between the open ends of two tubes placed face to face with each other. The air is choked at nozzle exit and a radial underexpanded jet is formed around the tubes. Both frontal and side views of the flow field are visualized simultaneously using the shadowgraph method. As the oblique shocks in the jet are formed surrounding the circular tubes, the ring-shaped shocks are visualized in the frontal view, the cell structure of the jet being in the side view. Oscillation of the flow field with many vortices and a feed-back mechanism of density waves around the jet obtained experimentally and numerically are discussed.