Investigation of vortex in pump sump by V3V measurements
Authors: Chao Liu , Xijie Song , Hang Wei , Jian Xu 
Published: January 2021

Abstract
The aims, scope and conclusions of the paper must be in a self-contained abstract of a single paragraph with 60-120 words. The abstract must be informative and not just indicative and contain a summary of the significant results reported in the paper. No references should be cited. Avoid mathematical expressions as far as possible. Just below the abstract, up to six keywords should be provided. The vortex may appear in the sump when the pump inlet is not properly designed or the pump suction pipe is not deeply submerged enough, not only will the pump’s energy performance and cavitation performance be significantly reduced, but it may also cause the pump unit to vibrate and fail to operate properly. The water surface vortex is the most common vortex into the sump, and it is also a vortex that has a great influence on the operation of the pump. According to the development process of the water surface vortex, it is divided into four shapes: A-shape vortex: the water flow rotates slowly, forming only a shallow sunken; the B-shape vortex: the water flow rotates faster, the sunken becomes deeper as a funnel, and the air intermittently enters the water pump. It has only influence on the performance of the pump; C-shape vortex: the rotation speed of the water flow is very fast, the funnel has penetrated into the suction pipe, the air continuously enters the water pump, and the pump unit generates strong vibration, which has a serious impact on the operation of the water pump; D-shape vortex: The water flow rotates sharply around the suction pipe. A large amount of air enters the water pump, and the pump unit generates severe vibration, which is impossible to operate. The pump unit generates severe vibration and cannot run. In this paper, the vortex of the sump is measured by the V3V volumetric field three-dimensional laser velocimetry to study the mechanism and development of vortex under the flow rate at the BEP of the pump. The measurement results show that the distribution of the circumferential velocity Vu of the vortex region in the vortex core is characterized by the value at the center of the core being close to zero, and the circumferential velocity of the vortex increasing with the increase of the radius, At a certain value the circumferential velocity is gradually reduced as the radius increased, and there is a maximum value during this change. At each stage of the development of the vortex, the regularity of the circumferential velocity of the vortex changes with the radius is the same that circumferential velocity increases in the vortex core, then decreases gradually outside of vortex core. The 3D vortex is obtained. The circumferential velocity gradient is quite large in the vortex core region. The maximum value is not on the water surface, but at a small depth below the water surface. The dissipation of vorticity is much rapid than its accumulation, which is shown as Instantaneous collapse of the vortex (less than 1 s). When the vorticity of the vortex reaches a certain value, it often causes severe vibration of the pump unit.