A Study on Shock Wave formed in Unsteady Jet through Vortex Ring

Abstract

If shock wave is discharged from an open pipe end, unsteady jet issues from it and a vortex ring occurs at an edge of pipe end. The vortex ring accelerates downstream and reaches a certain velocity at last. In the vortex ring going downstream, a core of vortex ring roles up a boundary of the unsteady jet so that a rearward-facing shock is formed in the vortex ring. The jet boundary interacts with the shock wave there, and then the weak pressure waves are scattered. The interaction is pointed out to be one of the sources of noise. As one of the examples, there is unsteady jet from an exhaust pipe of a reciprocating internal combustion engine or a reciprocating compressor. In order to clarify the mechanism that the shock-vortex interaction occurs, the unsteady jet from a circular pipe end is visualized by the shadowgraph method and analyzed.