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

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) 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.

Free‐Surface Turbulent Flow in an Eccentric Stirred Tank

“…The interfacial behavior was successfully captured. Yang and Zhou used the combination of Spalart‐Allmaras based DES and VOF model in the study of the free‐surface turbulent flow in a concentrically unbaffled dished‐bottom stirred tank. The superiority of DES in the prediction of the free‐surface hydrodynamics in stirred tanks was confirmed.…”

Industrial Case-Study-Based Computational Fluid Dynamic (CFD) Modeling of Stirred and Aerated Bioreactors

“…The model performs the calculation of one continuous phase, calculating the other one as a difference. This calculation approach guarantees a low computational cost under the restrictive hypothesis, verified in the present case unit, that the dispersed phase is less than 10% of the total. , Gas holdup in stirred fermenters can range from 1 to 20% . Therefore, the proposed approach is suitable for average gas rate sparged units. k-ω Menter’s shear stress transport (SST) for turbulence modeling, as it combines a robust formulation and near-wall region accuracy (imported by the k-ω model) with an independence from free flow in the bulk areas (guaranteed by the k-ε model).…”

“…This calculation approach guarantees a low computational cost under the restrictive hypothesis, verified in the present case unit, that the dispersed phase is less than 10% of the total. 32 , 33 Gas holdup in stirred fermenters can range from 1 to 20%. 34 Therefore, the proposed approach is suitable for average gas rate sparged units.…”

Digital Design of Batch Cooling Crystallization Processes: Computational Fluid Dynamics Methodology for Modeling Free-Surface Hydrodynamics in Agitated Crystallizers

“…A number of previous CFD studies have focused on the modeling of turbulent free-surface flow using the Volume-of-Fluid (VoF) method in unbaffled vessels agitated by radial-flow impellers (for example, Haque et al, Cartland Glover and Fitzpatrick, Haque et al, Yang et al, and Yang and Zhou) and in vessels with two beavertail baffles agitated by a RCI entering from the bottom , and compared the predictions with the measurements of components of mean velocity and turbulence kinetic energy. In these studies, using the Reynolds-averaged Navier-Stokes (RANS) approach, turbulence has been represented using the standard k- ε, ,,,− Shear-stress transport (SST), , and Reynolds-stress transport (RST) , models. In more recent studies, detached-eddy simulation (DES) , and large-eddy simulation (LES) , approaches have also been used.…”

“…In these studies, using the Reynolds-averaged Navier-Stokes (RANS) approach, turbulence has been represented using the standard k- ε, ,,,− Shear-stress transport (SST), , and Reynolds-stress transport (RST) , models. In more recent studies, detached-eddy simulation (DES) , and large-eddy simulation (LES) , approaches have also been used. The free-surface profiles and the mean velocity components are generally well predicted by both the RANS and DES/LES approaches; however, the turbulence kinetic energy in the impeller stream is underpredicted by the former method.…”