CFD simulation of stirred tanks: Comparison of turbulence models (Part II: Axial flow impellers, multiple impellers and multiphase dispersions)

Abstract

In the first part of the review, published literature regarding the CFD modelling of single-phase turbulent flow in stirred tank reactors with radial flow impellers was critically analysed. A brief overview of different turbulence models (standard k − ε model, RNG k − ε model, the Reynolds stress model and large eddy simulation) as well as impeller baffle interaction models has been presented in the previous part. This part is concerned with the review of literature regarding CFD simulation of axial flow impellers. Comprehensive simulations have been carried out using various turbulence models and the model predictions (of all the mean velocities, turbulent kinetic energy and its dissipation rate) have been compared with the experimental measurements at various locations in the tank. The strengths and weaknesses of various turbulence models for axial flow impellers is presented. The quantitative comparison of exact and modelled turbulence production, transport and dissipation terms has highlighted the reasons behind the partial success of various modifications of standard k − ε model as well as Reynolds stress model. Literature efforts on multiple impeller systems and multiphase systems have been discussed in a separate section. Based on these results, suggestions have been made for the future work in this area.Dans la première partie de l'étude, on a procédéà une analyse critique de la littérature concernant la modélisation de la dynamique des fluides numérique de l'écoulement turbulentà une phase dans les réacteursà cuve agitée dotés de turbinesàécoulement radial. Une vue d'ensemble rapide des différents modèles de turbulence (modèle standard k-e, modèle RNG k-e, modèle aux tensions de Reynolds et simulation des grandeś echelles), ainsi que des modèles d'interaction des déflecteurs de turbine, aété présentée dans la partie précédente. Cette partie se concentre sur l'analyse de la littérature concernant la simulation de DFN de turbinesàécoulement axial. Des simulations complètes ontété effectuées en utilisant plusieurs modèles de turbulence et les prédictions des modèles (de toutes les vitesses moyennes, de l'énergie cinétique turbulente et de son taux de dissipation) ontété comparées aux données expérimentales relevéesà différents endroits de la cuve. On a présenté les points forts et les points faibles de plusieurs modèles de turbulence concernant les turbinesàécoulement axial. La comparaison quantitative des données exactes et modélisées de la production, du transport et de la dissipation de la turbulence a mis enévidence les raisons qui expliquent la réussite partielle de plusieurs modifications apportées au modèle standard k-e ainsi qu'au modèle aux tensions de Reynolds. Une partie distincte est consacréeà la discussion des résultats indiqués dans la littérature concernant les systèmesà roues multiples et les systèmes multiphases. Sur la base de ces résultats, desétudesà venir dans ce domaine ontété suggérées.

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

“…[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]. The results of the CFD based on the RANS (Reynolds Averaged Navier Stokes) approach were formerly validated by the measurements of the mean values.…”

Models and Applications for Simulating Turbulent Solid–Liquid Suspensions in Stirred Tanks

“…In order to simulate turbulent continuous single-phase flows, three approaches are usually utilized: Reynolds averaged NavierStokes (RANS) simulation, large eddy simulation (LES), and direct numerical simulation (DNS). These approaches and their applications to stirred tanks have been reviewed in detail by Sommerfeld and Decker (2004), Van den Akker (2010), and Joshi et al (2011aJoshi et al ( , 2011b. The present section focuses on the models for simulating the influence of the discrete phase on the continuous phase in comparison with single-phase flows.…”

A Study of CFD Simulations of the Flow Pattern in an Agitated System with a Pitched Blade Worn Turbine

“…Table 2. Main characteristics of CFD computations in the investigated system (k = -4.33 ± 0.20, g = 0.667) The Reynolds stress simulation for the steady-state Multiple Reference Frame (MRF) approach was used with the standard wall function in the pilot plant mixing vessel (diameter D = 300mm) (Joshi et al, 2011). The other turbulence models were also examined and consequently not used for final computation because of their worse agreement with the experimental results.…”

“…The values of the impeller pumping capacities were selected to be reference values for the comparison of the CFD simulation with respect to the results of the experiments. It is worth mentioning, that the pumping capacity of impeller is a commonly used parameter for comparison of experimental data and CFD simulations by many authors (Joshi et al, 2011).…”