Numerical modeling of flow in chlorine disinfection tanks

The reliability of simulations of flow and disinfection processes in disinfection contact tanks is determined by the accuracy of computations in terms of the hydrodynamic characteristics in the tanks, particularly the accuracy of the calculations of advection and shear stress, which are two problematic terms currently under intensive research. As part of the development of a simulation module for a software package of flow and disinfection process predictions in chlorine contact tanks, various modeling methods and difference schemes have been tested for typical tank configurations, and the results are compared and analyzed. In the software the computation of shear stress terms was originally represented by a depth mean viscosity model, and its results have been compared with that of calculations using the (k) over bar-<(epsilon)over bar> and the Smagorinsky subgrid scale stress models in an attempt to improve upon the model predictions. The discretization of advection terms in the software module was a first-order upwind difference scheme, the results of which also have been compared with that of its two alternatives, the QUICK scheme and a third-order upwind difference scheme. Predictions made by using several combinations of these models and schemes were tested against measurements from a physical model study.