RELATIONSHIP BETWEEN UNSTEADY-FLOW, PRESSURE-FLUCTUATIONS, AND NOISE IN A CENTRIFUGAL PUMP .1. USE OF PDV DATA TO COMPUTE THE PRESSURE FIELD

Velocity distributions determined by using Particle Displacement Veloc imetry are used for computing the pressure field within the volute of a centrifugal pump. It is shown that blade-tongue interactions and non uniform outflux from the impeller are primary contributors to local pr essure fluctuations and far field noise. Consequently, a slight increa se in the space between the impeller and the tongue causes significant changes in flow structure and reductions in the resulting noise. The impact is significant as long as the tongue-impeller gap is less than 20 percent of the impeller radius. It is also shown that the vorticity distributions, particularly the large vortex trains associated with t he jet/wake phenomenon, nominate variations in the total pressure. Thu s, it is unlikely that a potential flow model can provide any realisti c description of the flow structure.