Effect of nozzle inlet geometry on underexpanded supersonic jet characteristics

Abstract

A numerical study has been undertaken on underexpanded sonic jets issuing from nozzles of varied inlet geometries. The Mach stem height in the jet issuing from the contoured nozzle has been the greatest over the range of pressure ratios investigated. A vena-contracta effect has been noted in the jet flow field in the cases of nozzles with sharp inlet geometries. The effect of the inlet geometry is to delay the onset of the typical barrel shock structure seen in underexpanded jets. The distortion of the jet boundary results in a smaller Mach stem for the same pressure ratio and exit Mach number.