Simulation of Flow in Stirred Vessels with Axial Flow Impellers: Effects of Various Numerical Schemes and Turbulence Model Parameters

The standard two-equation (k-e) turbulence model has been used to numerically simulate the flow in an agitated baffled cylindrical vessel with axial flow impellers. Three numerical schemes, namely, upwind scheme, hybrid scheme, and power-law scheme, were used to evaluate the competitiveness of the various schemes. The solutions were obtained by using the SIMPLE algorithm. The effects of initial guess values of the flow variables, the underrelaxation parameters, internal iterations, etc., on the rate of convergence were analyzed. The sensitivity of the model parameters on the flow characteristics was investigated thoroughly. Further, the effects of global grid sizes and near-wall grid sizes on the solution were also investigated. The boundary conditions in the impeller region for the velocities and turbulent kinetic energy were provided from the experimental data. However, for the energy dissipation rate, as iterative process was adopted taking the local information into account. Computations were carried out for six different impeller designs. It was found that the predicted values were qualitatively in good agreement with the experimental data.