STARTING JET–WALL INTERACTION

A flow starting from a shock tube is accompanied by a bow shock wave and a head ring vortex. This flow pattern is responsible for impulsive sound generation when the jet impinges on the wall. This problem is studied experimentally and theoretically in the present paper. In the experiment a conventional shock tube of internal diameter D=65 mm is used. The jet issuing from the shock tube was visualized by means of a Schlieren system. The instantaneous pressure was measured at the wall at several distances from the axis of the jet. Subsonic and slightly underexpanded jets with flow Mach numbers in the range from 0·65 to 1·14, were considered. It was found that the shock wave, after reflection at the wall, generates a toroidal sound wave due to its interaction with a ring vortex. The sound wave splits into two pressure pulses when it passes through the vortex core. The vortex alone generates a sound wave when it reaches the wall. The theoretical approach is based on the Euler equation. It allowed the authors to predict the main characteristics of the considered flow satisfactorily.