Numerical Investigation on the Flow Structure and Vortex Behavior at a Large Scale Pump Sump

Vortex in pump station sumps could lead to equipment operation with vibration and cavitations, and its impact is even stronger in large scale pump station sumps. In this study, the flow structure and vortex behavior in the sumps of a large scale pump station were investigated with a three dimensional CFD approach. The approach solves Reynolds averaged Navier-Stokes equations by the realizable k-ε turbulence model with wall function. The numerical simulations were carried out under three different water levels (low, standard and high) and three different pump operating combinations (operating with one, two or three pumps). The important flow feathers in the entire flow field such as submerged vortices, free-surface vortices were revealed. The strength and location of vortices under different operating conditions were presented. To reduce the vorticity magnitude in the sumps which would expand to affect the flow around pump inlet, effects of three different anti-vortex devices (DA, DB, and DC) for the pump station were also investigated numerically. It is found that the vortex attached to the floor has larger vorticity scale than that attached to side wall and back wall. The vorticity magnitude at higher sump water level is smaller than that at lower water level. The operation of multi pumps also has a strong impact to the flow patterns in sumps. Anti-vortex device DB has better performance than the two others, it decreases the floor attached and sidewall attached vortex and makes the pump inlet flow smooth.