A critical review of the published literature regarding the computational fluid dynamics (CFD) modelling of single-phase turbulent flow in stirred tank reactors is presented. In this part of review, CFD simulations of radial flow impellers (mainly disc turbine (DT)) in a fully baffled vessel operating in a turbulent regime have been presented. Simulated results obtained with different impeller modelling approaches (impeller boundary condition, multiple reference frame, computational snap shot and the sliding mesh approaches) and different turbulence models (standard k − ε model, RNG k − ε model, the Reynolds stress model (RSM) and large eddy simulation) have been compared with the in-house laser Doppler anemometry (LDA) experimental data. In addition, recently proposed modifications to the standard k − ε models were also evaluated. 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. A discussion is presented to highlight strengths and weaknesses of currently used CFD models. A preliminary analysis of sensitivity of modelling assumptions in the k − ε models and RSM has been carried out using LES database. 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 RSM. The volume integral of predicted energy dissipation rate is compared with the energy input rate. Based on these results, suggestions have been made for the future work in this area.Nous présentons un examen critique de la littérature concernant la modélisation de la dynamique des fluides numérique (DFN) de l'écoulement turbulentà une phase dans les réacteursà cuve agitée. Dans cette partie de l'examen, nous présentons les simulations de DFN de turbinesà ecoulement radial (principalement des turbinesà disque (TD)) dans un réservoir entièrement cloisonné effectuées dans un régime turbulent. Les résultats des simulations obtenus grâceà différentes approches de modélisation des turbines (couche limite turbulente, méthode des référentiels multiples, snap-shot de modélisation numérique, maillage glissant) età différents modèles de turbulence (modèle standard k-e, modèle RNG k-e, modèle aux tensions de Reynolds et simulation des grandeséchelles) ontété comparés aux données expérimentales internes d'allocation de Dirichlet latente (ADL). De plus, les modifications des modèles standards k-e récemment proposées ontégalementétéévaluées. Les prédictions du modèle (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. Une discussion présente les points forts et les points faibles des modèles de DFN actuellement utilisés. Une analyse préliminaire de la sensibilité des hypothèses de modélisation liées aux modèles k-e et RSM aété menée en utilis...

Crystallization is the primary process used to purify synthetic drug substances and intermediates as well as to control bulk properties, including particle size, surface area, and flowability. Accordingly, new or improved tools to aid crystallization design are of central importance to drug development. In this Perspective, we provide a brief review of the state of the art, identify current challenges, and highlight key opportunities within different aspects of crystallization process development for synthetic pharmaceutical compounds.

The published literature on the liquid-phase mixing in a turbulent flow regime has been critically reviewed and analyzed. Experimental techniques for mixing time have been described together with their relative merits. The effects of the impeller design (blade number, blade angle, blade and disk dimensions, and blade shape), the location of the impeller (off-bottom clearance, distance from the vessel center, i.e., eccentricity), and the vessel size on the liquid-phase mixing have been critically analyzed. The mixing performance dependency on the internals such as baffles (number, dimension, and position) and the draft tube has been presented in detail. Further, an extensive review on the mathematical models proposed for the liquid-phase mixing has been presented, and the utility of the computational fluid dynamics modeling for the mixing optimization has been illustrated. Finally, suggestions have been made for the selection of an energy-efficient impeller-vessel configuration, and directions have been given for future studies.