An experimental and theoretical study of converging shock waves

Authors: Apazidis, N., Lesser, M.B., Tillmark, N.T., Johansson, B
Document Type: Article
Pubstate: Published
Journal: Shock waves
Volume: 12   39-58
Year: 2002


A series of experiments on converging shocks in a thin cylindrical chamber filled with gas and with a specifically chosen form of the boundary have been performed. The main result of this study shows that it is possible to obtain polygonal shocks with sharp corners and plane sides by reflecting a cylindrical shock from a smooth boundary. The shock behavior in the vicinity of corner regions of a converging polygonal shock exhibits the major properties of the shock focusing process in general. One of the major difficulties encountered in modelling of this process is the fact that the shock reflected from the boundary will propagate into a a non-homogeneous flow field created by the initial shock. The theoretical and computational method, developed by Apazidis & Lesser (1996) and based on an extended form of Whitham`s theory of Geometrical Shock Dynamics (GSD), accounts for this feature and may therefore be applied to the present situation. Shock fronts computed on the basis of above theoretical and numerical procedure have shown to be in good agreement with the experimental results. Numerical calculations based on this method were also able to reproduce the major features of the experimental study of the shock focusing in a parabolic reflector by Sturtevant & Kulkarny (1976). It has been shown that the flow conditions ahead of the shock are of great importance for the focusing process and govern the flow pattern in the focusing region of the reflector.