Numerical simulation and modal analysis of vortices in a pump sump

Pump sumps are settling chambers for incoming flows prior to their removal by pumps. These pump sumps are widely used for drainage in pumping stations and power plants. During off-design operations, free surface and sub-surface vortices can appear in pump sumps, causing significant pump performance degradation and system vibrations. The present study is performed to obtain insights to develop an effective and highly robust vortex suppressing device for pump sumps. Large eddy simulations are conducted on a scaled model pump sump to reproduce the vortex flow field with free surface and sub-surface vortices. The vortical flow is investigated by proper orthogonal decomposition (POD) based on the velocity field to extract the key energetic features. The dominant POD modes near the suction pipe provide insights for understanding the complex vortex dynamics and developing a novel control device for the suppression of vortex appearances.