Numerical simulation of rectangular settling tanks

Abstract

A numerical model to simulate the performance of primary clarifiers, with emphasis on the prediction of the velocity field and concentration distribution, is presented. The model is restricted to those mean steady flows which are isothermal, neutral density, low in solids concentration and nearly two-dimensional. The model employs the Strip Integral Method (SIM) to solve the governing differential equations of continuity, momentum and mass transport. This method is an improvement over the plug flow models in that it can reproduce the main features of the flow such as the boundary layer, recirculation and distribution of the dispersion coefficient. It has an advantage over the finite element and the finite difference models since it requires relatively low computer storage and computational time. The hydrodynamic submodel was calibrated using measured velocity distribution in a physical model. The model was used to simulate the rectangular clarifiers used in the City of Sarnia, Ontario, Canada. The predict...