Numerical Study of the tongue geometry effects on the cavitation and performance of a centrifugal pump in off-design conditions

In this study, the effects of the volute tongue geometry variation on the head, efficiency, velocity distribution and cavitation structure of a centrifugal pump in the steady flow behavior under off-design conditions have been investigated. Numerical simulation modeling based on the  turbulence model with a hybrid grid is used to simulate the flow within the modeled pump. The flow is simulated by means of a commercial Computational Fluid Dynamics (CFD) software that solved the Reynolds-averaged Navier-Stokes (RANS) equations for a three-dimensional steady flow. The effects of thickness and angle of the tongue in various flow rates on the pump performance is investigated. Numerical results which are in well agreement with the experimental ones, show that the higher tongue angles caused an improvement on the head and efficiency of the pump especially in high flow rates. Investigations also indicate that the tongue thickness variations have no significant impact on the pump performance, although, the lower the thickness, the better the overall pump performance.