A previous paper has reported measurements of dynamic force on a disc valve, during the opening of the valve, and has shown that significant differences are to he found between this true dynamic force and the corresponding force measured under steady state conditions at increments of valve displacement. In this paper, the authors describe an investigation of the velocity field around the same disc valve, again measured dynamically during the rise of the valve. The measurement uses miniature 45 sensor probes, in a constant temperature hot wire anemometry technique, to define the instantaneous velocity vectors, and analysis of the signals from the wires is by a fully calibrated method developed by the authors for this project. It is shown that entrained gas from above the valve plays a significant part in the development of flow patterns, and that the development of eddies from discontinuities in the surface of the valve seat (eg from ring seats) is, on a time scale, of the same order as that of the rise time of the valve. Analysis is confined to the assumption that flow is in radial planes.
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