Modeling Turbulent Flow in Stirred Tanks with CFD: The Influence of the Modeling Approach, Turbulence Model and Numerical Scheme

摘要

Single phase turbulent flow in a tank stirred by a down- and an up-pumping pitched blade turbine has beenudsimulated using CFD. The effect of the modeling approach, discretization scheme and turbulence model on meanudvelocities, turbulent kinetic energy and global quantities, such as the power and circulation numbers, has beenudinvestigated. The results have been validated by LDV data. The stationary and time-dependent modelingudapproaches were found to have little effect on the turbulent flow, however the choice of the numerical schemeudwas found to be important, especially for the predicted turbulent kinetic energy. A first order method was foundudto highly underestimate LDV data compared with higher order methods. The type of the turbulence model wasudlimited to the k-e and RNG models due to convergence difficulties encountered with a Reynolds Stress Modelud(RSM) and there was found to be little effect of these models on the mean flow and turbulent kinetic energy.udThis latter quantity was found to be largely under predicted in the discharge region of the down-pumpingudimpeller in comparison with LDV data. Better agreement was found for the up-pumping pitched blade turbine.udEstimated power numbers were found generally to be in good agreement for the down- and up-pumping data.udHowever, the circulation number tended to be over predicted by about 30% and 40% for the down- and uppumpingudagitators, respectively.