Formes d'une vésicule en géométrie confinée (thèse: 2012 - 2015)
Publications scientifiques au M2P2
J Gubspun, C De Loubens, R Trozzo, Johnny Deschamps, M Georgelin, et al.. Perturbations of the flow induced by a microcapsule in a capillary tube. Fluid Dynamics Research, IOP Publishing, 2017, 49 (3), ⟨10.1088/1873-7005/aa6270⟩. ⟨hal-01590334⟩ Plus de détails...
Soft microcapsules moving in a cylindrical capillary deform from quasi-spherical shapes to elongated shapes with an inversion of curvature at the rear. We investigated the perturbation of the flow by particle tracking velocimetry around deformed microcapsules in confined flow. These experiments are completed by numerical simulations. Microcapsules are made of a thin membrane of polymerized human albumin and their shear elastic moduli are previously characterized in a cross flow chamber. Firstly, the velocity of the microcapsule can be calculated by theoretical predictions for rigid spheres, even for large deformations as 'parachute- like' shapes, if a relevant definition of the ratio of confinement is chosen. Secondly, at the rear and the front of the microcapsule, the existence of multiple recirculation regions is governed by the local curvature of the membrane. The amplitudes of these perturbations increase with the microcapsule deformation, whereas their axial extents are comparable to the radius of the capillary whatever the confinement and the capillary number. We conclude that whereas the motion of microcapsules in confined flow has quantitative similitudes with rigid spheres in terms of velocity and axial extent of the perturbation, their presence induces variations in the flow field that are related to the local deformation of the membrane as in droplets.
J Gubspun, C De Loubens, R Trozzo, Johnny Deschamps, M Georgelin, et al.. Perturbations of the flow induced by a microcapsule in a capillary tube. Fluid Dynamics Research, IOP Publishing, 2017, 49 (3), ⟨10.1088/1873-7005/aa6270⟩. ⟨hal-01590334⟩
R. Trozzo, G. Boedec, M. Leonetti, M. Jaeger. Axisymmetric Boundary Element Method for vesicles in a capillary. Journal of Computational Physics, Elsevier, 2015, 289, pp.62-82. ⟨10.1016/j.jcp.2015.02.022⟩. ⟨hal-01281961⟩ Plus de détails...
The problem of a vesicle transported by a fluid flow can present a large range of length scales. One example is the case of a vesicle producing a tether, and eventually pearls, in an elongational flow. Another case occurs when a lubrication film is formed, such as during the short range interaction between two vesicles. Such problems are still challenging for 3D simulations. On the other hand, a good understanding could be obtained by first considering the axisymmetric regime when such a regime exists. An axisymmetric model could then be used, without the criticisms that can be made of a 2D approach. We propose such a model, primarily interested in flows through narrow cylindrical capillaries. Two options are compared, with and without explicit representation of the capillary boundaries by a mesh. The numerical effort is characterized as a function of the vesicle’s initial shape, the flow magnitude and the confinement. The model is able to treat typical configurations of red blood cells flowing through very narrow pores with extremely thin lubrication films.
R. Trozzo, G. Boedec, M. Leonetti, M. Jaeger. Axisymmetric Boundary Element Method for vesicles in a capillary. Journal of Computational Physics, Elsevier, 2015, 289, pp.62-82. ⟨10.1016/j.jcp.2015.02.022⟩. ⟨hal-01281961⟩