Numerical prediction of the effect of free surface vortex air-entrainment on sediment erosion in a pump

Abstract

Sediment erosion through synergetic effects between free surface vortex (FSV) and particle erosion in silt-laden flow seriously affects the safe operations of pump. The purpose of this paper is to study the influence of free surface vortex entrainment on the erosion inner the pump impeller, aimed at the FSV and sediment erosion in sediment laden flow in a pump station of Yellow River, a new Eulerian-Lagrange approach was applied to simulate the sediment-laden flow by combining the Lagrange particle tracking approach and Volume of Fluid (VOF) method, followed by the application of Tabakoff model to estimate the erosion. Volume of fluid method was used to simulate the continuous flow FSV, and Lagrange method the particle trajectory. The theoretical model and filed results on site were used to verify the reliability of the proposed approach. Free surface vortex on particle motion and microscopic interactions between air and erosion were reviewed and discussed. Combined with the theoretical analysis and calculation results, the particle impact angle in the impeller was analyzed, and the erosion types were defined. Air entrainment by FSV does not directly erode the impeller components, but mainly changes the position, the local velocity and the concentration of the particles, which aggravates the sediment erosion in the impeller. Interestingly, air entrainment can reduce the surface erosion at some instantaneous moments. The present work may provide important engineering insights to resolve the erosion.