Prediction of flow pattern in stirred tanks: new constitutive equation for eddy viscosity

Abstract

The CFD simulations were carried out for the flow produced by two axial flow impellers, namely a pitched-blade downflow turbine (PBTD, N_p = 2.1) and a hydrofoil impeller (N_p = 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_μ 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. 1989, 81, 225), zonal model of Sahu et al. (Ind. Eng. Chem. Res. 1998, 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.