Dynamic Evolution of a Transient Supersonic Trailing Jet Induced by a Strong Incident Shock Wave

TL;DR

This study investigates the complex transient behavior of a supersonic jet from a pulse detonation engine, revealing unique shock structures and developing a model to explain the formation of a second triple shock point.

Contribution

It introduces a pseudo-steady model for transient shock conditions and uncovers the mechanism behind the formation of a second triple shock in a transient supersonic jet.

Findings

Identification of a second triple shock configuration in transient jets

Development of a pseudo-steady model for shock conditions

Mechanism linking vortex motion to shock formation

Abstract

The dynamic evolution of a highly underexpanded transient supersonic jet at the exit of a pulse detonation engine is investigated via high-resolution time-resolved schlieren and numerical simulations. Experimental evidence is provided for the presence of a second triple shock configuration along with a shocklet between the reflected shock and the slipstream, which has no analogue in a steady-state underexpanded jet. A pseudo-steady model is developed, which allows for the determination of the post-shock flow condition for a transient propagating oblique shock. This model is applied to the numerical simulations to reveal the mechanism leading to the formation of the second triple point. Accordingly, the formation of the triple point is initiated by the transient motion of the reflected shock, which is induced by the convection of the vortex ring. While the vortex ring embedded shock move essentially as a translating strong oblique shock, the reflected shock is rotating towards its steady state position. This results in a pressure discontinuity that must be resolved by the formation of a shocklet.