Three-Dimensional Simulation of Air Entrainment in a Sump Pump

The three-dimensional unsteady vortex flow in a sump pump is investigated by the computational fluid dynamics (CFD) method with the shear-stress transport (SST) k - omega model and the volume of fluid (VOF) multiphase model. The helicity density, involving both velocity and vortex, is especially used to discuss the mechanism of the process for air entrainment. The calculated results are qualitatively validated compared with the vortex observed in a previous experiment. The results investigated show that the helicity density takes a very important role in forming the process of the air entrainment. When the dimple appears, the helicity density near the intake pipe is larger than that close to the surface. When the air begins to flow into the pipe, the helicity density tube close to the surface reaches a certain level to connect the helicity density tube from the intake pipe. Moreover, the air entrainment can be suppressed if the helicity density tube is broken by placing a circular plate in a certain position. (C) 2017 American Society of Civil Engineers.