Unsteady numerical calculation of an entire multistage pump was performed by using a large eddy simulation (LES) at the design flow rate to investigate the flow field in the pump in detail and to evaluate the accuracy of LES by comparing the results with an experimental and a conventional CFD result based on a Reynolds-averaged Navier-Stokes (RANS) equation. We investigated a four-stage centrifugal pump consisting of a suction bend, impellers, vaned diffusers, return channels, and a discharge volute. The interaction between the impeller and the stator was taken into account by using a moving overset grid in LES calculations, and the flow field in the inlet portion of each hydraulic part was investigated using the calculated result. In the experimental investigation, velocity distributions and pressure fluctuation were measured at several points by using a scaled model pump. RANS calculation was performed with respect to a single-stage pump composed of the first-stage component of the four-stage pump. We found that the hydraulic design of the four-stage pump is satisfactory and that LES was a very effective design tool for investigating the flow field in detail including the unsteadiness in the hydraulic passageway of the multistage pump.

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