Large‐Eddy Simulation of Unsteady Flow in a Mixed‐Flow Pump

Abstract

This article describes the large‐eddy simulation (LES) of the internal flows of a high–specific‐speed, mixed‐flow pump at low flow‐rate ratios over which measured head‐flow characteristics exhibit weak instability. In order to deal with a moving boundary interface in the flow field, a form of the finite‐element method in which overset grids are applied from multiple dynamic frames of reference has been developed. The method is implemented as a parallel program by applying a domain‐decomposition programming model. The predicted pump heads reproduce the instability and agree fairly well with their measured equivalents, although the predicted stall takes place at a flow‐rate ratio that is a few percentage points lower than the measurements. The phase‐averaged distributions of the meridional‐ and tangential velocity components at the impeller′s inlet and exit cross sections were also compared with those measured by laser‐Doppler velocimetry. Reasonably good agreements have been obtained between the computed and measured profiles. The developed LES program thus seems to be a promising design tool for a high–specific‐speed, mixed‐flow pump, particularly for off‐design evaluations.