Numerical simulation of air entrainment and suppression in pump sump

The dynamics of air entrainment and suppression schemes in a pump sump are investigated. Four different turbulence models (standard k-epsilon model, realizable k-epsilon model, renormalization group (RNG) k-epsilon model and shear-stress transport (SST) k-omega model) and the volume of fluid (VOF) multiphase model are employed to simulate the three-dimensional unsteady turbulent flow in a pump sump. The dynamic processes of air entrainment are simulated under conditions of relatively high discharge and low submergence; the mechanism of air entrainment is discussed in detail. Then suppression means for air entrainment is adopted by placing a circular plate on the intake pipe at three different heights. The results show: the position and structure of the free-surface vortices, sidewall-attached vortices, back wall-attached vortices, and floor-attached vortices calculated by SST k-omega turbulence model agree well with the experimental data. The two main contributors for air entrainment are pressure difference and vortex strength. By placing a circular plate in the middle of the intake pipe under water, air entrainment is suppressed because vortex strength is reduced.