Measurement of Transient Flowrates in Oil Column Separation

Oil column separation in which a tensile wave and the consequent rupture of an oil column can be observed provides intriguing information with cavitation study. In order to investigate the phenomena in more detail from this viewpoint, it is essential to secure a means to precisely measure transiently changing flowrates in column separation. The present paper has aimed to achieve this object; the method is based on detecting pressure differences kinematically induced in an unsteady pipe flow. Instead of a conventional pressure difference transducer, two independent pressure gauges are used to pick up the pressure differences with high fidelity. Theoretically predicted step-like flowrates until the column rejoining have been successfully measured, showing the usefulness of the method. It is also pointed out that the algorithm adovocated by ZHAO et al. to conveniently transform sampled pressure difference data to flowrate can give unreasonable results when the transient is fast.