Prediction of Flow Pattern in Stirred Tanks:  New Constitutive Equation for Eddy Viscosity

The CFD simulations were carried out for the flow produced by two axial flow impellers, namely a pitched-blade downflow turbine (PBTD, N<INF>p</INF> = 2.1) and a hydrofoil impeller (N<INF>p</INF> = 0.34) by the impeller boundary condition approach. The tank was fully baffled, and the flow regime was turbulent. An attempt has been made to develop a new constitutive equation for C<INF>μ</INF> in the description of eddy viscosity given by a standard k−ε model. The resulting predictions with the new eddy viscosity relation are compared with the experimental data. Also the comparison is sought with the predictions of impeller boundary condition approach using k−ε model with the standard and modified turbulence parameters (Ranade et al. Chem. Eng. Commun. <BO>1989</BO>, 81, 225), zonal model of Sahu et al. (Ind. Eng. Chem. Res. <BO>1998</BO>, 37, 2116) and the sliding mesh simulation using a standard k−ε model. For all these cases, energy balance has been established and compared with the experimental data. This paper also presents a critical review of the computational fluid dynamic (CFD) studies pertaining to the prediction of the flow produced by the axial flow impellers.