Simulation of flow in stirred vessel with axial flow impeller: zonal modeling and optimization of parameters

Abstract

The usefulness of the turbulent k-ε model for simulation of flow in a stirred vessel was studied in detail. For optimization, the effects of model parameters on flow characteristics were analyzed. It was observed that, any single set of model parameters could not yield even reasonable agreement between the model predictions and the experimental observations throughout the vessel. Therefore, the concept of zonal modeling was introduced for the r-z plane. It was observed that with the introduction of zonal modeling, the predicted values of flow variables, except the energy dissipation rate, were in good agreement with experimental data even close to the top surface of the tank. The same results could not be obtained with the standard set of parameters and a single zone. Local turbulent energy dissipation rate (ε ) was calculated using the expression (ε = k^3/2/L_res) proposed by Wu and Patterson (1989). The zonal modeling prediction was better than the prediction by a standard set of parameters. However, above the impeller, a wide discrepancy between the predicted and experimental value for energy dissipation rate was observed.