References of "Calvo, Sébastien"
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See detailSolid-liquid suspension of microcarriers in stirred tank bioreactor - Experimental and numerical analysis
Delafosse, Angélique ULiege; Loubière, Céline; Calvo, Sébastien ULiege et al

in Chemical Engineering Science (in press)

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See detailAnalysis of PIV measurements using modal decomposition techniques, POD and DMD, to study flow structures and their dynamics within a stirred-tank reactor
de Lamotte, Anne ULiege; Delafosse, Angélique ULiege; Calvo, Sébastien ULiege et al

in Chemical Engineering Science (2018)

The present work is a comparative analysis of Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) computed on experimental turbulent velocity fields measured in a 20L-tank stirred ... [more ▼]

The present work is a comparative analysis of Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) computed on experimental turbulent velocity fields measured in a 20L-tank stirred by two Rushton impellers at two rotating speeds, N = 150 and 300 rpm. POD identifies flow structures that optimally capture the total kinetic energy of the flow, while DMD identifies structures that significantly contribute to the dynamics of the flow. The experimental data, i.e. the instantaneous radial and axial velocity fields, come from 2-D Particle Image Velocimetry (PIV). The flow motion is turbulent, and it occurs over a wide range of length and time scales, from equipment-dependent large-scale coherent structures to the smallest-scale eddies where energy dissipation takes place. It thus provides an interesting benchmark case for the comparison between POD and DMD, which are based on energy and dynamic analysis, respectively. POD analysis reveals that the most energetic structures are related to the inherent periodic unsteadiness due to the relative motion between the rotating impeller blades and the non-moving baffles. Apart from the mean field, the first most energetic group of modes is related to trailing vortices induced by the Rushton turbines and is associated to a frequency equivalent to the blade passage frequency and its overtones. The second most energetic group of modes is related to vortical structures in the impeller stream and is associated to a frequency equivalent to the rotating speed. DMD analysis identifies flow structures that are found similar to these most energetic modes, although differences appear due to the fact that DMD isolates structures associated to a single frequency and their corresponding growth/decay rate. As in POD, the relative importance of each DMD mode can be estimated using an appropriately defined energy criterion. Comparison of the results from both modal decomposition methods points out their complementarity and their potential for describing the spatial and time characteristics of the flow within a stirred tank. [less ▲]

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See detailInvestigating the effects of hydrodynamics and mixing on mass transfer through the free-surface in stirred tank bioreactors
de Lamotte, Anne ULiege; Delafosse, Angélique ULiege; Calvo, Sébastien ULiege et al

in Chemical Engineering Science (2017), 172

In stirred-tank bioreactors, flow structures of various length and time scales are implied in scalar transport phenomena, such as gas species transfer through the liquid free-surface and their ... [more ▼]

In stirred-tank bioreactors, flow structures of various length and time scales are implied in scalar transport phenomena, such as gas species transfer through the liquid free-surface and their homogenization in the bulk. A proper understanding of the underlying mechanisms, i.e. hydrodynamics, mixing and mass transfer, and of their interactions is required to design and develop reliable and efficient production-scale bioprocesses. The objective of the present work is to experimentally investigate the coupling between gas-liquid mass transfer of oxygen with mixing efficiency and circulation patterns inside an arbitrarily chosen stirred-tank configuration aerated through the liquid free-surface, a baffled 20 L-vessel agitated by two Rushton turbines. Based on global parameter values, the most appropriate rotating speed, N = 300 rpm, is selected in order to further study local hydrodynamic quantities using Particle Image Velocimetry (PIV), as well as mixing and mass transfer dynamics using Planar Laser-Induced Fluorescence (PLIF). The results obtained with these local experimental methods are analyzed in detail. Their averages are first successfully compared to global data. Statistical analysis of their spatial distributions show that large-scale flow patterns significantly influence mass transfer through the free-surface of the stirred tank. Even if global measurements show that global characteristic times for mixing and mass transfer differ by two orders of magnitude, local experimental characterization shows persistent vertical gradients of dissolved gas concentrations. So the dissolved gas concentration is not as perfectly uniform as one might expect. [less ▲]

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See detailApproche par modèle de compartiments pour la modélisation des bioréacteurs
Delafosse, Angélique ULiege; Calvo, Sébastien ULiege; Toye, Dominique ULiege

Scientific conference (2017, November 09)

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See detailLarge-Eddy Simulations of microcarrier exposure to potentially damaging eddies inside mini-bioreactors
Collignon, Marie-Laure ULiege; Delafosse, Angélique; Calvo, Sébastien ULiege et al

in Biochemical Engineering Journal (2016)

Mechanically stirred vessels equipped with rotating impellers generate heterogeneous transitional or turbulent flows. However, some cells as animal or human mesenchymal stem cells (hMSC) adhered on ... [more ▼]

Mechanically stirred vessels equipped with rotating impellers generate heterogeneous transitional or turbulent flows. However, some cells as animal or human mesenchymal stem cells (hMSC) adhered on microcarriers, are reputed sensitive to hydromechanical stresses arising from stirring. Many publications, especially using Computational Fluid Dynamics, characterize spatial fields of velocity and turbulence inside bioreactors but the exposure frequency to these stresses is never taken into account in the case of animal cell culture bioreactor description. To fill this gap, this study used both CFD Reynolds-Averaged and Large-Eddy Simulations to characterize the hydrodynamics inside 250 mL mini-bioreactors, which is a relevant volume for hMSC cultures. Five impeller geometries were studied. From the velocity and turbulence fields calculated, an energy dissipation/circulation function, related to both frequency and intensity of potentially damaging hydrodynamic events for the cells, was determined for various operating conditions. Based on the simulation results, the marine propeller operating in up-pumping mode seems to be the most adapted condition, since it exhibits a low frequency of exposure to an acceptable intensity of the turbulent dissipation rate. From a general point of view, the new methodology proposed should be used in the future to screen the most adapted bioreactor geometry to biological constraints. [less ▲]

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See detailEuler–Lagrange approach to model heterogeneities in stirred tank bioreactors – Comparison to experimental flow characterization and particle tracking
Delafosse, Angélique ULiege; Calvo, Sébastien ULiege; Collignon, Marie-Laure ULiege et al

in Chemical Engineering Science (2015), 134

The aim of this work is the validation of an Euler–Lagrange modeling approach coupling a CFD-based compartment model (Eulerian approach) and a stochastic model based on a Continuous-Time Markov Chain ... [more ▼]

The aim of this work is the validation of an Euler–Lagrange modeling approach coupling a CFD-based compartment model (Eulerian approach) and a stochastic model based on a Continuous-Time Markov Chain (Lagrangian approach). The turbulent flow structure and the mixing process in a bioreactor stirred by an axial Mixel TT impeller is characterized by PIV and tracer experiments. Comparison between experimental and numerical data shows that the CFD-based compartment model is able to reproduce accurately the spatial heterogeneities inside the bioreactor. The trajectory of a small tracer particle which perfectly follows the fluid flow is measured by optical trajectography. It is then simulated by a stochastic model which is either based on an homogeneous or on an inhomogeneous Continuous Time Markov Chain (CTMC). Comparison of residence and circulation time distributions in three zones defined inside the bioreactor shows that the inhomogeneous CTMC model predicts with an excellent accuracy the particle trajectories inside the bioreactor. The modeling approach proposed here could be an useful tool to design scale-down bioreactors in order to reproduce at lab-scale the stress levels encountered in large-scale production bioreactors and to characterize and compare different bioreactor configurations. [less ▲]

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See detailHydrodynamics, mixing and mass transfer in baffled stirred tanks
de Lamotte, Anne ULiege; Delafosse, Angélique ULiege; Calvo, Sébastien ULiege et al

Conference (2015, September 24)

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See detailSurface aeration in baffled stirred tanks: hydrodynamics, mixing and mass transfer characteristics
de Lamotte, Anne ULiege; Delafosse, Angélique ULiege; Calvo, Sébastien ULiege et al

Poster (2015, September)

Biotechnological and chemical processes often need a supply of gas for acceptable product formation. In some applications - where either gas requirements/reactor volumes are relatively low, or bubbles are ... [more ▼]

Biotechnological and chemical processes often need a supply of gas for acceptable product formation. In some applications - where either gas requirements/reactor volumes are relatively low, or bubbles are undesirable - aeration through the liquid free-surface is enough to meet the demand. In case of sparged stirred tanks, aeration through the liquid free-surface is a factor to be determined when scaling-up /down processes. Gas-liquid transfer is strongly influenced by the hydrodynamic conditions. Two phenomena, occurring at different scales, can be coupled in order to explain mass transfer : (i) circulation (macroscale) and (ii) mixing/homogenization (microscale). Mixing/homogenization takes into consideration the small eddies responsible for the rippled liquid free-surface and for the concentration gradients surrounding it. Circulation determines the fluid path across the reactor as well as its contribution of the surface aeration and leads to periodic and local deformation of the liquid free-surface. Circulation also accounts for the design of the reactor, where the scaling problems are focused. The objective of this work is to develop an experimental approach able to fully (global and local quantities) characterize a chosen agitation configuration in terms of hydrodynamics, mixing and transfer, in order to assess the capability of computational methods to predict gas-liquid mass transfer due to aeration through the liquid free-surface. [less ▲]

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See detailHydrodynamics, mixing and mass transfer in baffled stirred tanks
de Lamotte, Anne ULiege; Delafosse, Angélique ULiege; Calvo, Sébastien ULiege et al

in Proceedings of the 15th European Conference on Mixing (2015, June)

The present work presents CFD simulations of hydrodynamics, mixing and mass transfer in a surface-aerated baffled stirred tank. The modelling of the multiphase flow is realized via an Euler-Euler approach ... [more ▼]

The present work presents CFD simulations of hydrodynamics, mixing and mass transfer in a surface-aerated baffled stirred tank. The modelling of the multiphase flow is realized via an Euler-Euler approach. Three closure models are tested for the resolution of the RANS equations. When fully-developed flow field is reached, gas-liquid transfer is implemented with a local mass transfer coefficient estimated by the eddy cell model, and the temporal evolution of dissolved gas concentration is predicted.Hydrodynamic and mixing quantities as well as mass transfer parameters for the different turbulence models are compared with experimental data available for the same geometrical and operating features. A critical analysis of the prediction results allow to assess the models capabilities and to highlight the possible critical issues of the simulations. [less ▲]

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See detailVALIDATION OF AN EULER-LAGRANGE COMPARTMENT MODEL FOR THE DESIGN OF SCALE-DOWN BIOREACTOR USED IN ANIMAL CELL CULTURES
Delafosse, Angélique ULiege; Calvo, Sébastien ULiege; Collignon, Marie-Laure ULiege et al

in Proceeding of the 15th European Conference on Mixing (2015, June)

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See detailHYDRODYNAMICS IN A DISPOSABLE RECTANGULAR PARALLELEPIPED STIRRED BIOREACTOR WITH ELLIPTIC PENDULUM MOTION PADDLE
Collignon, Marie-Laure ULiege; Droissart, Laurent; Delafosse, Angélique ULiege et al

in Biochemical Engineering Journal (2015), 93

Stainless steel bioreactors increasingly fall behind to their disposable counterparts in pharma research as they do not require cleaning or sterilization. This led company ATMI LifeSciences to develop the ... [more ▼]

Stainless steel bioreactors increasingly fall behind to their disposable counterparts in pharma research as they do not require cleaning or sterilization. This led company ATMI LifeSciences to develop the “Nucleo™”. Original in design, this disposable bioreactor comprises a rectangular parallelepiped plastic bag stirred by a paddle revolving in elliptic pendulum motion. Studies covering this bioreactor showed good homogeneity of culture medium as well as good productivity for animal cell cultures. To further explain these good performances, the flow inside the “Nucleo™” had to be resolved. This paper focuses on the mean flow description, computed from stereo-PIV measurements performed in 20 verticals covering the whole volume of a 50 dm3 Nucleo™ bioreactor. As the flow is already turbulent in the chosen agitation conditions, its dimensionless mean velocity field does not vary with the paddle rotational speed. Mean flow pattern exhibits an axial symmetry – same flow is observed in opposite quarters of the tank – and can be described as a three-dimensional helix coiled on itself to form a distorted horizontal torus which covers the whole tank volume. Mean velocity value is on average doubled in the cone swept by the paddle, and its two horizontal components are twice higher than its vertical ones. However, mean velocity remains significant everywhere and, in particular, no stagnant area is observed in tank corners. Our results thus confirm previous studies observations. [less ▲]

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