An experimental and comparative study of jet penetration in supersonic flow.

Abstract

A series of experiments was conducted in which H^ or N2 was injected at Mach numbers of 1.00, 1.31, 1.50, and 1.67 from a nozzle in a flat plate transversely into a Mach 2.72 free airstream. The structure of the emergent jet was recorded in schlieren photographs, and injectant concentration profiles at several locations in the near downstream (x/dj* < 10) region from gas samples. Normalized penetration was found to be governed by both the ratio of the jet pressure to an effective back pressure (behind a shock in the airstream) and the ratio of jet to freestream momentum. Absolute penetration was not substantially increased by increasing the stagnation pressure of the sonic jets, but was increased by going to supersonic injection. Both underexpanded sonic jets and supersonic jets produced normal shocks (Mach disks) in the emergent flow. The location of the Mach disk in the sonic injection tests was correlated with similar results of sonic injection into a quiescent medium. An analytical relationship based on a solid-body-drag model (equivalent inclined cylinder) best described the maximum concentration trajectory in the near downstream region where the effect of coaxial mixing has not yet become appreciable.