Near acoustic field and shock structure of rectangular supersonic jets

Abstract

An underexpanded supersonic rectangular jet is studied experimentally at a pressure ratio range of 1-15. The shock-cell and shear-layer structure variation with the pressure ratio is shown to be related to the near-field pressure fluctuations. Near the sonic, fully adapted velocity, the jet is fully symmetric. An abrupt change to a flapping mode occurs at a low Mach number, causing a large increase in the spreading rate, which is also related to the appearance of an upstream propagating screech component