Flow Separation Inside a Supersonic Nozzle Exhausting into a Subsonic Compressible Crossflow

Surface pressure data were acquired along the nozzle wall and surrounding the exit plane for an axisymmetric supersonic jet exhausting transversely from a flat plate into a subsonic compressible crossflow. These measurements showed that the backpressure is sufficient to instigate nozzle flow separation under flowfield conditions that may be found in flight. The separation line was found to be axially asymmetric, which results from the angular variation in the backpressure on the nozzle generated by the jet's interaction with the freestream. As either the jet-to-freestream momentum ratio or the crossflow freestream Mach number is independently reduced, the size of the separated flow region becomes larger because the backpressure on the nozzle is increased relative to the jet stagnation pressure. Schlieren imaging is consistent with these observations and provides further elucidation of the resulting jet shock wave structure. Comparison of the data to correlations derived from freejet separation data is possible by employment of these predictions in a piecewise fashion around the perimeter of the nozzle. (Author)