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

摘要

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.