On the driver-reservoir technique Part 1 Application to shock and gun tunnels Part 2 Determination of optimum reservoir size

Abstract

The driver-reservoir technique, first proposed by Henshall et al, is of interest to shock tunnel users because of its promise of an increase in running time. The most usual form of termination of running time in the shock tunnel is by the arrival, at the end plate, of the head of the rarefaction wave which results from the rupture of the main diaphragm. In the driver-reservoir technique, the head of the rarefaction wave interacts with a perforated plate, at the end of the high pressure chamber, which separates this chamber from a larger diameter vessel called the reservoir. Under certain conditions this results in no waves propagating downstream except Mach waves. The head of the expansion wave has therefore been effectively eliminated and this will result in an increase in running time. In this paper an account of the driver-reservoir technique is given, together with various theoretical analyses. A simple model is proposed which describes the wave processes within the reservoir, and the increase in running time to be expected from various Sizes of reservoir. From this model it is shown that the most important reservoir dimension is the diameter. Experiments from the NPL 2 in. shock tunnel are presented, and the application of the technique to gun tunnels is discussed.