Shock Wave Focusing in a Vertical Annular Shock Tube

Abstract

Converging cylindrical and spherical shock waves are particularly useful for producing high temperatures and pressures at the center of convergence. The efficiency of this method of generation of high temperatures and pressures depends on the stability of the converging shock wave. However, the stability of the converging shock wave is a difficult problem to analyse since the behaviour of the converging shock wave is primarily dependent on nonlinear characteristics. When the stability of converging shock waves is discussed from the viewpoint of the effects of growth of initial disturbances on final shock wave convergence, it is first necessary to generate converging shock waves free of initial disturbances.

In the present study, in order to clarify the stability of converging cylindrical shock waves, a vertical diaphragmless co-axial annular shock tube, which can generate a converging cylindrical shock wave with minimal disturbances, was designed and built. Paper reports the performance of this vertical annular shock tube: it is found, by double exposure image holographic interferometric flow visualization, that cylindrical shock waves converge more uniformly towards the center than in a similar co-axial annular shock tube with supporting struts. Further, the behavior of converging cylindrical shock waves with given initial disturbances was clarified.