Abstract
The present study analyzes pump sump flows with various discharges and gate submergence. Investigations using a three-dimensional large eddy simulation model and an acoustic Doppler velocimeter are performed. Flow patterns and velocity profiles in the approaching flow are shown to describe the flow features caused by various discharges and gate submergence. The variation of a large-scale spanwise vortex behind a sluice gate is examined and discussed. The suction effect on approaching flow near the pipe column is examined using numerical modeling. To gain more understanding of the vortices variation, a comparison between time-averaged and instantaneous flow patterns is numerically conducted. Additionally, swirl angle, a widely used index for evaluating pump efficiency, is experimentally and numerically examined under various flow conditions. The results indicate that the pump becomes less efficient with increasing discharge and gate submergence. The fluctuation of the free surface over the pump sump is also discussed.
Highlights
Large-scale pumps with capacities of 1–10 m3/s are extensively used in circulating cooling system for electric power plants, flood-control systems, and sewage-treatment plants
The inflow and outflow boundary conditions were velocity Dirichlet boundary conditions, which specify a determined value on a specific surface and give rise in flow-in or flow-out boundary, that is, uniform flow condition given at the approaching flow inlet and intake-pipe outlet
To obtain the stable solution, the standard von Neumann stability analysis states that Cr defined as Max(|u|)(δt/dς), where δt is the time step restricted by the advection term and dς is a measure of cell size, should be between 0.5 and 0.85
Summary
Large-scale pumps with capacities of 1–10 m3/s are extensively used in circulating cooling system for electric power plants, flood-control systems, and sewage-treatment plants. There are some guidelines for engineering applications, including the “The Hydraulic Design of Pump Sumps and Intakes” published by the British Hydromechanics Research Institute [7] and the “American National Standard for Pump Intake Design” [8] Flow problems, such as vortices induced by a fluid passing through obstructions, can remarkably reduce pump efficiency or even damage pump components [9, 10]. Chuang and Hsiao [5] numerically studied the same issue [4] by including the effect of fluid viscosity and more realistic simulation conditions Their results showed that viscosity affects the prediction of flow patterns and that the streamwise velocity can be better captured by including cross flow (i.e., considering a larger domain) instead of imposing a given boundary condition. The free surface fluctuation in the pump sump is examined
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