This study shows the capability of computational fluid dynamics in capturing the unsteady flow inside a centrifugal pump. The studied object is an industrial centrifugal water pump (NS=32) with backward blades and a vane-less single tongue volute. To obtain numerical solution, the Reynolds averaged Navier-Stokes equations (RANS) has been discretized on a three-dimensional unstructured grids using finite volume co-located method. To correlate the pressure and velocity fields, the SIMPLE algorithm was used. To exert the boundary conditions in the impeller-volute interface, the sliding mesh technique has been employed and a new method has been presented to facilitate the interpolation involved. Using the developed code, the internal flow of the mentioned pump was investigated in design and off-design capacities and in several positions of the impeller. Time averaged results are compared with the experimental performance curve and good agreement is found. Besides, the amplitude of the fluctuating pressure in the volute at the blade passing frequency is successfully captured. At design conditions, the flow is well conducted by the volute, and the impeller works smoothly in a nearly balanced pressure distribution at its outlet. At off-design conditions, however, there is a considerable difference among the flows between various blades and pressure distribution on the impeller periphery is unbalanced. In a few words, the main achievement of the work is providing the modeling possibilities for prediction of incompressible flow and the dynamic interaction of the impeller and the volute in centrifugal pumps and fans.
