Study of the formation and dynamic characteristics of the vortex in the pump sump by CFD and experiment

The formation mechanism and the dynamic characteristics of the floor-attached vortex(FAV)in the pump sump are analyzed,with the velocity gradient as the key factor.The FAV is shown to be formed when the velocity gradient in the singular point area reaches a certain strength.The evolution of the FAV is accompanied by the energy accumulation and dissipation in the vortex area.The generated FAV is in the form of the vortex pair at the initial stage,with opposite directions of rotation.The vortex with the same rotating direction as the impeller is strong because the rotational kinetic energy is easy to accumulate.The circumferential velocity of the FAV first increases and then decreases with the radius of the vortex core,indicating the FAV is a kind of forced vortex.The radius with the largest velocity gradient is the radius of the vortex core.