Numerical Simulation of the Optimal Impeller Radius in An Oxidation Ditch

Abstract

Impellers are the main power source for oxidation ditches. An impeller radius has an important influence on the flow field structure in an oxidation ditch channel. The effect of the size of impeller radius on the structure of flow fields in an oxidation ditch was studied by using the two-phase gas-liquid model and the 3D Realizable k-e turbulence model. The PISO( Pressure-Implicit with Splitting of Operators) algorithm was used for the solution of velocity and pressure. The VOF( Volume Of Fluid) method was used to simulate water free surface. The concept of optimal radius ratio was introduced to analyze the simulation results. When the ratio of the impeller radius to the diameter of the oxidation ditch channel bend,r / d was 0. 218,the percentage of the fluid with velocity greater than 0. 3m / s to the entire fluid was the greatest,and that the length of the backflow region in the straight channel was the shortest. The ratio of impeller radius to the diameter of an oxidation ditch channel bend,r / d with a value of 0. 218,is called the optimal impeller radius ratio.