Free Surface Turbulent Flow in an Unbaffled Stirred Tank: Detached Eddy Simulation and VOF Study

F. L. Yang and S. J. Zhou

Abstract
Numerical simulations based on the RANS model are known to have drawbacks of low accuracy in predicting the turbulence quantities of the flow fields in stirred tanks. For this purpose, the detached eddy simulation (DES) model was employed to simulate the turbulent flow in an unbaffled dish-bottom stirred tank. The free-surface deformation was modelled by the volume of fluid (VOF) method. The numerical predictions were validated with LDV measurements reported by Haque et al. (Haque, J. N., Mahmud, T., Roberts, K. J., Liang, J. K., White, G., Wilkinson, D., Rhodes, D., Can. J. Chem. Eng. 89 (2011) 745)11. The results show that the predicted surface profiles using the combination of DES and VOF are generally better than their counterparts obtained by the k-ε model. The mean velocity components and turbulent kinetic energy are in good agreement with the experimental results. By comparison, the differences between the k-ε predictions and the LDV data are much greater. These findings indicate that DES works better than k-ε model in the prediction of the free-surface hydrodynamics in stirred tanks.

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Keywords
stirred tank, free surface flow, turbulence, detached eddy simulation (DES), volume of fluid (VOF)