The Instability of Axisymmetric Supersonic Jet Impinging on Flat Plate

摘要

The interaction between an under-expanded supersonic jet and a flat plate with the plate located in the region in which the plate produces shock waves and flow fluctuations was investigated. A sonic nozzle was used in part one of the project to investigate the differences between results from two previous studies. Although the results of the present work differed from both of the two earlier studies, they agreed very well with theoretical predictions by the method of characteristics. A Mach 2.2 nozzle was used in the second part of the project to determine the magnitude and frequency of pressure pulsations on the plate, and the effect of an acoustic lining around the outside of the nozzle. It was found that the maximum peak-to-peak fluctuating pressure was about 1.13 of the mean plate pressure, at a separation distance of 1.5 nozzle exit diameters and a nozzle pressure ratio of 12. The acoustic lining was found to reduce the magnitude of fluctuating pressure by a factor of about one third.