Procédés et mécanique aux petites échelles PROMETHEE
Micro-objets déformables sous forçage hydrodynamique
Microfluidique et Procédés
Organisation des écoulements aux petites échelles
Séparations membranaires
suite...
Présentation
L’équipe PROcédés et MEcanique aux petiTes écHEllEs (PROMETHEE) développe des compétences marquées relevant aussi bien de la mécanique des milieux continus que du génie des procédés tout en combinant approche expérimentale et développement de théories et de modèles. L’originalité des études menées se décline selon plusieurs spécificités :
Echelle micro-nano d’observation et d’analyse qui évacue les problématiques liées à la turbulence (régime de Stokes) mais nécessite de considérer des aspects aux frontières de la discipline ;
Rôle prédominant des interfaces : interactions avec les parois solides à l’échelle nano (nano-tubes), interaction fluide-structure avec des membranes fluides ou polymérisée à l’échelle méso ;
Connexion avec les fluides complexes, la matière molle et les systèmes biologiques.
Sur le thème de la micro- et nano-fluidique, les objets d’étude, physico-chimiques (gouttes, capsules,…) et biologiques (vésicules, globules rouges,…), comprennent aussi les procédés intensifiés d’encapsulation et de vectorisation par microréacteur, thèmes en plein essor. L’équipe développe également des outils de caractérisation de l’organisation aux petites échelles comme le développement de simulations numériques pour rendre compte de la ségrégation obtenue au sein de milieux granulaires et la mise au point de méthode chimique de caractérisation des effets de micromélange (mélange à l’échelle moléculaire). A cela s’ajoute une activité de caractérisation et modélisation thermodynamique de milieux complexes.
Les outils numériques développés et mis en œuvre sont variés : intégrale de frontière, éléments finis, immersed boundary method, méthode Lattice Boltzman…
Sudip Das, Marc Jaeger, Marc Leonetti, Rochish M. Thaokar, Paul G. Chen. Effect of pulse width on the dynamics of a deflated vesicle in unipolar and bipolar pulsed electric fields. Physics of Fluids, American Institute of Physics, 2021, 33 (8), pp.081905. ⟨10.1063/5.0057168⟩. ⟨hal-03317441⟩ Plus de détails...
Giant unilamellar vesicles subjected to pulsed direct-current (pulsed-DC) fields are promising biomimetic systems to investigate the electroporation of cells. In strong electric fields, vesicles undergo significant deformation, which strongly alters the transmembrane potential, consequently the electroporation. Previous theoretical studies investigated the electrodeformation of vesicles in DC fields (which are not pulsed). In this work, we computationally investigate the deformation of a deflated vesicle under unipolar, bipolar, and two-step unipolar pulses and show sensitive dependence of intermediate shapes on type of pulse and the pulse width. Starting with the stress-free initial shape of a deflated vesicle, which is similar to a prolate spheroid, the analysis is presented for the cases with higher and lower conductivities of the inner fluid medium relative to the outer fluid medium. For the ratio of inner to outer fluid conductivity, σ r = 10, the shape always remains prolate, including when the field is turned off. For σ r = 0.1, several complex dynamics are observed, such as the prolate-to-oblate (PO), prolate-to-oblate-to-prolate (POP) shape transitions in time depending upon the strength of the field and the pulse properties. In this case, on turning off the field, a metastable oblate equilibrium shape is seen, that seems to be a characteristics of a deflated vesicle leading to POPO transitions. When a two-step unipolar pulse (a combination of a strong and a weak subpulse) is applied, a vesicle can reach an oblate or a prolate final shape depending upon the relative durations of the two subpulses. This study suggests that the transmembrane potential can be regulated using a bipolar pulsed-DC field. It also shows that the shapes admitted in the dynamics of a vesicle depends upon whether the pulse is unipolar or bipolar. Parameters are suggested wherein, the simulation results can be demonstrated in experiments.
Sudip Das, Marc Jaeger, Marc Leonetti, Rochish M. Thaokar, Paul G. Chen. Effect of pulse width on the dynamics of a deflated vesicle in unipolar and bipolar pulsed electric fields. Physics of Fluids, American Institute of Physics, 2021, 33 (8), pp.081905. ⟨10.1063/5.0057168⟩. ⟨hal-03317441⟩
Simon Gsell, Umberto d'Ortona, Julien Favier. Lattice-Boltzmann simulation of creeping generalized Newtonian flows: theory and guidelines. Journal of Computational Physics, Elsevier, 2021, 429, pp.109943. ⟨10.1016/j.jcp.2020.109943⟩. ⟨hal-03166492⟩ Plus de détails...
The accuracy of the lattice-Boltzmann (LB) method is related to the relaxation time controlling the flow viscosity. In particular, it is often recommended to avoid large fluid viscosities in order to satisfy the low-Knudsen-number assumption that is essential to recover hydrodynamic behavior at the macroscopic scale, which may in principle limit the possibility of simulating creeping flows and non-Newtonian flows involving important viscosity variations. Here it is shown, based on the continuous Boltzmann equations, that a two-relaxation-time (TRT) model can however recover the steady Navier-Stokes equations without any restriction on the fluid viscosity, provided that the Knudsen number is redefined as a function of both relaxation times. This effective Knudsen number is closely related to the previously-described parameter controlling numerical errors of the TRT model, providing a consistent theory at both the discrete and continuous levels. To simulate incompressible flows, the viscous incompressibility condition M a 2 /Re 1 also needs to be satisfied, where M a and Re are the Mach and Reynolds numbers. This concept is extended by defining a local incompressibility factor, allowing one to locally control the accuracy of the simulation for flows involving varying viscosities. These theoretical arguments are illustrated based on numerical simulations of the two-dimensional flow past a square cylinder. In the case of a Newtonian flow, the viscosity independence is confirmed for relaxation times up to 10 4 , and the ratio M a 2 /Re = 0.1 is small enough to ensure reliable incompressible simulations. The Herschel-Bulkley model is employed to introduce shear-dependent viscosities in the flow. The proposed numerical strategy allows to achieve major viscosity variations, avoiding the implementation of artificial viscosity cutoff in high-viscosity regions. Highly non-linear flows are simulated over ranges of the Bingham number Bn ∈ [1, 1000] and flow index n ∈ [0.2, 1.8], and successfully compared to prior numerical works based on Navier-Stokes solvers. This work provides a general framework to simulate complex creeping flows, as encountered in many biological and industrial systems, using the lattice-Boltzmann method.
Simon Gsell, Umberto d'Ortona, Julien Favier. Lattice-Boltzmann simulation of creeping generalized Newtonian flows: theory and guidelines. Journal of Computational Physics, Elsevier, 2021, 429, pp.109943. ⟨10.1016/j.jcp.2020.109943⟩. ⟨hal-03166492⟩
Jinming Lyu, Paul G. Chen, G. Boedec, M. Leonetti, Marc Jaeger. An isogeometric boundary element method for soft particles flowing in microfluidic channels. Computers and Fluids, Elsevier, 2021, 214, pp.104786. ⟨10.1016/j.compfluid.2020.104786⟩. ⟨hal-02476945v2⟩ Plus de détails...
Understanding the flow of deformable particles such as liquid drops, synthetic capsules and vesicles, and biological cells confined in a small channel is essential to a wide range of potential chemical and biomedical engineering applications. Computer simulations of this kind of fluid-structure (mem-brane) interaction in low-Reynolds-number flows raise significant challenges faced by an intricate interplay between flow stresses, complex particles' in-terfacial mechanical properties, and fluidic confinement. Here, we present an isogeometric computational framework by combining the finite-element method (FEM) and boundary-element method (BEM) for an accurate prediction of the deformation and motion of a single soft particle transported in microfluidic channels. The proposed numerical framework is constructed consistently with the isogeometric analysis paradigm; Loop's subdivision elements are used not only for the representation of geometry but also for the membrane mechanics solver (FEM) and the interfacial fluid dynamics solver (BEM). We validate our approach by comparison of the simulation results with highly accurate benchmark solutions to two well-known examples available in the literature, namely a liquid drop with constant surface tension in a circular tube and a capsule with a very thin hyperelastic membrane in a square channel. We show that the numerical method exhibits second-order convergence in both time and space. To further demonstrate the accuracy and long-time numerically stable simulations of the algorithm, we perform hydrodynamic computations of a lipid vesicle with bending stiffness and a red blood cell with a composite membrane in capillaries. The present work offers some possibilities to study the deformation behavior of confining soft particles, especially the particles' shape transition and dynamics and their rheological signature in channel flows.
Jinming Lyu, Paul G. Chen, G. Boedec, M. Leonetti, Marc Jaeger. An isogeometric boundary element method for soft particles flowing in microfluidic channels. Computers and Fluids, Elsevier, 2021, 214, pp.104786. ⟨10.1016/j.compfluid.2020.104786⟩. ⟨hal-02476945v2⟩
Cláudio Fonte, David Fletcher, Pierrette Guichardon, Joelle Aubin. Simulation of micromixing in a T-mixer under laminar flow conditions. Chemical Engineering Science, Elsevier, 2020, 222, pp.115706. ⟨10.1016/j.ces.2020.115706⟩. ⟨hal-02892241⟩ Plus de détails...
The CFD simulation of fast reactions in laminar flows can be computationally challenging due to the lack of appropriate sub-grid micromixing models in this flow regime. In this work, simulations of micromixing via the implementation of the competitive-parallel Villermaux/Dushman reactions in a T-micromixer with square bends for Reynolds numbers in the range 60–300 are performed using both a conventional CFD approach and a novel lamellae-based model. In the first, both the hydrodynamics and the concentration fields of the reaction species are determined directly using a finite volume approach. In the second, the hydrodynamic field from the CFD calculations is coupled with a Lagrangian model that is used to perform the chemical reactions indirectly. Both sets of results are compared with previously published experimental data and show very good agreement. The lamellar model has the advantage of being much less computationally intensive than the conventional CFD approach, which requires extremely fine computational grids to resolve sharp concentration gradients. It is a promising solution to model fast chemical reactions in reactors with complex geometries in the laminar regime and for industrial applications.
Cláudio Fonte, David Fletcher, Pierrette Guichardon, Joelle Aubin. Simulation of micromixing in a T-mixer under laminar flow conditions. Chemical Engineering Science, Elsevier, 2020, 222, pp.115706. ⟨10.1016/j.ces.2020.115706⟩. ⟨hal-02892241⟩
Jiupeng Du, Nelson Ibaseta, Pierrette Guichardon. Generation of an O/W emulsion in a flow-focusing microchip: importance of wetting conditions and of dynamic interfacial tension. Chemical Engineering Research and Design, Elsevier, 2020, ⟨10.1016/j.cherd.2020.04.012⟩. ⟨hal-02799613⟩ Plus de détails...
6 To date, there is no information on the microfluidic emulsification of dibutyl adipate and 7 n-butyl acetate in water. Since these solvents are very suitable for microencapsulation by 8 interfacial polymerization, it is highly necessary to study the emulsification behavior of these 9 solvents in microchannel. This work shows that the microfluidic emulsification of these sol-10 vents in water may fail to obtain stabilized flow regimes. This is due to droplet coalescence 11 and wall wetting, even if a hydrophilic microchip is used. Hydrodynamic results show that 12 squeezing and dripping regimes are especially affected because of the wall wetting by the 13 dispersed phase. This difficulty can be circumvented by adding a surfactant (here Tween 14 80) into the aqueous phase. However, high surfactant concentrations (ten times the crit-15 ical micelle concentration) should be used for the water-dibutyl adipate system. Indeed, 16 comparison of flow maps for several surfactant concentrations seems to indicate that the 17 dynamic interfacial tension is higher than the one expected (equilibrium), for surfactant 18 concentrations lower than one hundred times the critical micelle concentration. The esti-19 mated diffusion time of Tween 80 is compared to the droplet formation time at different 20 conditions. The choice of more appropriate dimensionless numbers to represent flow maps 21 is also discussed. 22
Jiupeng Du, Nelson Ibaseta, Pierrette Guichardon. Generation of an O/W emulsion in a flow-focusing microchip: importance of wetting conditions and of dynamic interfacial tension. Chemical Engineering Research and Design, Elsevier, 2020, ⟨10.1016/j.cherd.2020.04.012⟩. ⟨hal-02799613⟩
Mercredi 16 juin 2021
- De la vague déferlante au globule rouge / Soutenance HDR Paul Gang CHEN
Dr. Paul Gang CHEN
Date de soutenance : le mercredi 16 juin à 15h00 (visio - Zoom)
Résumé : au cours de cette soutenance, je présenterai mes différents travaux sur la modélisation et la simulation numérique d’écoulements interfaciaux : de la vague déferlante au globule rouge.
Jury :
M. Daniel Henry, LMFA, École Centrale de Lyon, Rapporteur
M. Grétar Tryggvason, Johns Hopkins University, Rapporteur
M. Stéphane Zaleski, d’Alembert, Sorbonne Université, Rapporteur
M. Richard Saurel, LMA, Aix-Marseille Université
M. Marc Jaeger, M2P2, École Centrale de Marseille, Tuteur
M. Marc Leonetti, LRP, Grenoble, Invité
Mardi 16 Mars
- Preparation of polyurea microcapsules calibrated in size and shell thickness by a microfluidic process for the absorption of ultraviolet / Soutenance de thèse Jiupeng DU
Doctorant : Jiupeng DU
Date de soutenance : le mardi 16 mars à 14h00 en VISIO
Abstract : This thesis aims to exploit the advantages of microfluidics for the production of polyurea microcapsules. Because of its ability to produce drops with a very narrow size distribution, microfluidic emulsification shows great interest as the first step for rapid interfacial polymerisation. Although the literature on the production of drops in microchannels is abundant, commonly used organic solvents are limited to certain toxic hydrocarbon oils or ketones, as these solvents are very hydrophobic and therefore easy to emulsify in water.
The first part of the work concentrates on the feasibility of emulsifying two less hydrophobic green solvents (dibutyl adipate and n-butyl acetate) in water and study the different flow regimes within a hydrophilic flow-focusing microchannel of glass. The results show that the wetting of the walls by dibutyl adipate can be modified by adding a surfactant (Tween 80). However, the formation of the drops being much faster than the transfer of the surfactant to the interface of the drop being formed, concentrations much higher than the critical micellar concentration are necessary to avoid wetting of the walls by the dispersed phase and thus the appearance of disordered flow regimes. The behavior of the n-butyl acetate/water system is similar, but the comparison of the flow maps for the two systems raises the question of the choice of dimensional numbers for representing the transition between the dripping and jetting regimes.
In the second part, the addition of an interfacial polymerization within the emulsion formed by microfluidics is studied in detail. We aim to fabricate polyurea microcapsules calibrated in size and shell thickness containing octyl salicylate (OS). These microcapsules are used to study, for the first time, the influence of the shell thickness of microcapsules on their absorption efficiency against ultraviolet (UV) light. The results show that an increase of the concentration of isocyanate (HDB-LV or hexamethylene diisocyanate biuret) in the organic phase increases the shell thickness of the microcapsules, their encapsulation efficiency and very moderately their average absorbance. The average absorbance of the microcapsules is inversely proportional to the size of the microcapsules (for the same mass of OS). A theoretical model is proposed to estimate the average absorbance as a function of the mass fraction of HDB-LV in the organic phase and of the size of microcapsules. Finally, the concentration of amine (ethylenediamine) has been optimized to ensure the spherical shape of the microcapsules.
Jury:
Marc LEONETTI (CNRS, LRP), Rapporteur
Nathalie LE SAUZE (Univ Toulouse III), Rapportrice
