Some non-equilibrium effects in depressurization experiments on water-filled systems

Early work used a straight constant diameter pipe, with a glass bursting disc at one end to initiate depressurization. Such a system gives the fastest rate of depressurization possible in one-dimensional flow and provides a base point for theoretical studies. Later tests used a reservoir behind a long pipe, so that the effects of a recompression wave on the early flow could be examined. Because local pressure measurements do not give enough information about the flow field to enable theoretical models to be assessed properly, the possibility of carrying out other transient measurements was carefully studied. It was decided that a density measurement, based on the attenuation of an X-ray beam passing through the pipe system, was the most practical additional measurement that could be taken. Such a measurement does not disturb the flow, but as it does not provide a cross-sectional area average value, there are some limitations in comparison with theoretical calculations. In the final series of tests, using a pipe of 206 mm internal diameter, it proved to be possible to use five beams of X-rays fanned out to cover the cross-section of the pipe so that a reasonable area mean value could be estimated. In this paper, a first attempt is made to summarize the information and discuss some first impressions that have been formed regarding the test information