RELATIONSHIP BETWEEN UNSTEADY-FLOW, PRESSURE-FLUCTUATIONS, AND NOISE IN A CENTRIFUGAL PUMP .2. EFFECTS OF BLADE-TONGUE INTERACTIONS

Maps of pressure distributions computed using PDV data, combined with noise and local pressure measurements, are used for identifying primar y sources of noise in a centrifugal pump. In the vicinity of the impel ler pressure minima occur around the blade and near a vortex train gen erated as a result of non-uniform outflux from the impeller. The press ure everywhere also varies depending on the orientation of the impelle r relative to the tongue. Noise peaks are generated when the pressure difference across the tongue is maximum, probably dire to tongue oscil lations, and when the, wake impinges on the tip of the tongue.