Auteur/autrice : LP

contact : ulysse.delabre@u-bordeaux.fr and antoine.aubret@u-bordeaux.fr

Modeling the flow of fibers interacting with grains

Mixtures of fibers and grains are present in many materials. Raw earth constructions often include a significant proportion of fibers or straw. In the materials and pharmaceutical industries, nanocellulose fibers are used as additives to powders. In civil engineering, synthetic fibers, or geotextiles, are used to stabilize embankments and banks. Lastly, when recycling materials that include fibers (wood, glass or carbon fibers), a grinding step is generally performed before separating the fibers and granular constituents. Figure : Example of simulation of fibers confined in a grain bed (discrete element method). In these different examples, fibers make a major contribution to the mechanical strength of materials, notably via their intrinsic properties (length, stiffness, breaking point), their collective behavior through entanglement effects or the formation of cohesive aggregates. In this thesis, numerical simulations by discrete element method (DEM) will be used to investigate mixtures of fibers and grains. The packing and rheology of these systems will be studied, and the effects of the proportion of fibers and grains, fiber stiffness, friction, confining pressure and shear rate will be investigated. The structural and dynamical properties of the simulated systems will be computed in order to understand the collective mechanisms of segregation and entanglement between deformable fibers. The simulation results will complement and be compared with experimental data obtained in the context of a partnership with experimental groups in the Paris area. The candidate will be part of the PhyProDiv group which has a strong expertise in the numerical modeling of granular media and soft matter and collaborates on these topics with other Physics (L2C) and Mechanics (LMGC) groups in Montpellier. We seek a candidate with a strong background in physics, mechanics or applied mathematics. Experience and interest in numerical modelling and simulation will be highly appreciated. Ability to work in a team and good communication skills are important as the PhD student will work in close contact within a project involving several research groups (in Sorbonne Université Paris, CNRS and Saint Gobain). The PhD is fully funded through an ANR grant (ConFig ANR-23-CE30-0032), and will take place at UMR IATE in Montpellier, south of France. For more details on the project, motivated and qualified candidates are encouraged to apply using the contacts mentioned below and to send a CV and motivation letter.

References

– Vo, T. T., Nezamabadi, S., Mutabaruka, P., Delenne, J. Y., & Radjai, F. (2020). Additive rheology of complex granular flows. Nature communications, 11(1), 1476.

– Fakih, M., Delenne, J. Y., Radjai, F., & Fourcaud, T. (2019). Root growth and force chains in a granular soil. Physical Review E, 99(4), 042903.

– Rakotonirina, A. D., Delenne, J. Y., Radjai, F., & Wachs, A. (2019). Grains3D, a flexible DEM approach for particles of arbitrary convex shape—Part III: extension to non-convex particles modelled as glued convex particles. Computational Particle Mechanics, 6, 55-84.

Contacts : Jean-Yves Delenne, jean-yves.delenne@inrae.fr Virginie Hugouvieux, virginie.hugouvieux@inrae.fr