Initial flow in a shock tube.

The well-known idealised theory of the simple shock-tube predicts values of the various flow properties, many of which are in good accord with experimental observations particularly for cases involving only weak shocks. Important departures from the above predictions can occur however, both in the flows at considerable distances from the diaphragm and those in its immediate vicinity. The former are mainly attributable to the finite opening-time of the dipahrgam while the latter arise chiefly as a result of the boundary layer which develops at the walls of the tube; both these mechanisms are ignored in ideal shock-tube theory. The present work is concerned principally with the initial stages of the flow and its chief aim is to determine the influence of the dynamic behaviour of the diaphragm on the flows developing in the tube. An experimental and theoretical study has been made of the static and dynamic behaviour of shock-tube diaphragms; the information obtained from this has been incorporated into a computer-formulation of the initial flow in the tube. Experimental measurements have been made which provide confirmation of many of the computed results, particularly in regard to shock trajectories, shock-formation distances and pressure histories in the vicinity of the diaphragm during the opening process