Detached eddy simulation on the turbulent flow in a stirred tank

Abstract

A detached eddy simulation (DES), a large‐eddy simulation (LES), and a k‐ε‐based Reynolds averaged Navier‐Stokes (RANS) calculation on the single phase turbulent flow in a fully baffled stirred tank, agitated by a Rushton turbine is presented. The DES used here is based on the Spalart‐Allmaras turbulence model solved on a grid containing about a million control volumes. The standard k‐ε and LES were considered here for comparison purposes. Predictions of the impeller‐angle‐resolved and time‐averaged turbulent flow have been evaluated and compared with data from laser doppler anemometry measurements. The effects of the turbulence model on the predictions of the mean velocity components and the turbulent kinetic energy are most pronounced in the (highly anisotropic) trailing vortex core region, with specifically DES performing well. The LES—that was performed on the same grid as the DES—appears to lack resolution in the boundary layers on the surface of the impeller. The findings suggest that DES provides a more accurate prediction of the features of the turbulent flows in a stirred tank compared with RANS‐based models and at the same time alleviates resolution requirements of LES close to walls. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3224–3241, 2012

Study of fluid flow in baffled vessels stirred by a Rushton standard impeller

“…To reduce the computational cost as well as to provide a good prediction of turbulent flows, containing boundary layers, Spalart et al [28] proposed a turbulence hybrid model-detached eddy simulation (DES) that transfers LES to a RANS-based simulation in boundary layers. Probably the first who used DES to predict flow field inside a tank stirred by a Rushton turbine were Gimbun et al [14]. They compared k-ε, standard LES and DES models and they uncovered a great potential for DES in predicting accurately the turbulent flow in a stirred tank.…”

Evaluation and accuracy of the local velocity data measurements in an agitated vessel

“…Although the development of mixing processes is nowadays based mostly on CFD (Computational Fluid Dynamics) where the LES (Large Eddy Simulation) approach is commonly used e.g. [1], [2], [3], [4], [5], the DNS (Direct Numerical Simulation) approach is also under development [6]. The large part of published results in this field were summarised in [7], [8].…”

An Investigation into Different Power Consumption Parameters of Rushton Turbines: A Computational Survey

“…The power consumption, P, can be calculated in a stirred tank from the torque acting on the impeller [23] by: …”