Study on the Noise Generated from Underexpanded Free and Impinging Jet

Abstract

This study is concerned with an underexpanded free jet flowing from an axisymmetric convergent nozzle and its impingement on a flat plate placed perpendicular to the jet axis. In the experiment, shadow photography was used to visualize the flow field and the sound pressure level of the noise generated in the jet was measured. As a result, the relation between the location and shape of the plate shock in the jet and the nozzle-plate spacing was established. Furthermore, we found how the sound pressure level of the noise changes with the jet structure, or the nozzle-plate spacing.