On the Dynamics of Imploding and Exploding Spherical Shock Wave Inside a Shock Tube

TL;DR

This study numerically investigates the focusing of spherical shock waves in a shock tube, examining the effects of viscosity, temperature variation, and flow structures like mushroom formations and vortices.

Contribution

It provides detailed numerical analysis of shock wave focusing, including flow structures, temperature changes, and reactive gas behavior, highlighting the role of viscosity and shock dynamics.

Findings

Formation of mushroom-shaped structures behind reflected shocks

Higher temperature inside mushroom structures compared to behind reflected shock

Flow inside mushroom structures is a reactive gas mixture

Abstract

The present work aims to study the phenomenon of shock wave focusing and the effect of viscosity in it. The focusing is achieved with a shock tube and a converging section attached to it. The converging section transforms the planar shock into a spherical shock and focuses it into a confined area. A shock of an initial strength Ms=2.94 has been chosen for the present studies. A detailed numerical study of the focusing region shows the formation of a mushroom-shaped structure behind the reflected shock and vortex formation. This was visualised through numerical shadowgraph images and by tracing the streamlines in the flow field. A study on the variation in temperature is carried out in order to have a quantitative assessment. It was found that the temperature inside the mushroom structure is higher than that behind the reflected shock. The study of species mass fraction in this region is also made. The flow inside the mushroom structure was found to be a reactive mixture of gas slug.