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Master 2: International Centre for Fundamental Physics
INTERNSHIP PROPOSAL Laboratory name: LadHyX CNRS identification code: UMR 7646 Internship director’surname: Blaise DELMOTTE, Camille DUPRAT, Gabriel AMSELEM e-mail: [email protected] Web pages: https://sites.google.com/site/blaisedelmotte/
http://www.off-ladhyx.polytechnique.fr/people/duprat/Home.html http://www.off-ladhyx.polytechnique.fr/people/amselem/index.html
Internship location: Ecole Polytechnique Thesis possibility after internship: YES Funding: Very likely If YES, which type of funding: ANR or Doctoral School
Simulating transport and clogging of elastic fibers in structured environments
Context : The growth and dispersal of biofilms in soils, catheters and capillaries occurs in complex media that are structured by interfaces, suspended particles or obstacles. These obstacles act as hydrodynamic and geometric traps that disturb the transport of particles and their hydrodynamic interactions. Crowded environments promote the formation of large elastic filaments of biofilm, called streamers. Streamers can detach and migrate in capillaries (Fig. 1a), which results to spread in secondary sites, clogging and worsening of infections [1]. The transport of streamers, the dispersal of biofilms and the migration of parasites in biological environments happen at low Reynolds number. In this regime, the dynamics of flexibles objects results from the complex interplay between the external flow, internal elastic stresses, contact forces and hydrodynamic interactions with the walls and the embedded obstacles. The combination of these effects can lead to the stoppage of the elastic particles in the network. Once blocked, a clump of biofilm can clog the whole channel due to its rapid growth [2]. Preliminary experiments, led by C. Duprat and G. Amselem, have shown that elastic fibers advected by a uniform flow can clog in periodic lattices of posts (Fig. 1b-c). Identifying the regimes for which clogging happens is essential to prevent infections.
Objectives : The goal of this internship is to use numerical simulations to identify the parameters (elastic fiber properties, flow magnitude, lattice spacing) that lead to clogging. The numerical method relies on the methods developed by B. Delmotte [3,4] to model flexible fibers and rigid obstacles in flows. The intern will start with simple situations with one fiber and one obstacle to test the numerical method against experiments. She/he will eventually extend the existing numerical tool to simulate the complete setup with periodic, quasi-periodic, self-similar and disordered patterns of posts. Candidates must have a solid background in Solid/Fluid Mechanics and Numerical Methods. [1] Hall-Stoodley, L., Costerton, J. W., & Stoodley, P. (2004). Nature reviews microbiology, 2(2), 95. [2] Drescher, K., Shen, Y., Bassler, B. L., & Stone, H. A. (2013). Proceedings of the National Academy of Sciences, 110(11), 4345-4350. [3] Delmotte, B., Climent, E., & Plouraboué, F. (2015). Journal of Computational Physics, 286, 14-37. [4] Balboa Usabiaga, F., Kallemov, B., Delmotte, B., Bhalla, A., Griffith, B., & Donev, A. (2017). Communications in Applied Mathematics and Computational Science, 11(2), 217-296 Condensed Matter Physics: YES Macroscopic Physics and complexity: YES Quantum Physics: NO Theoretical Physics: YES
Going through
Clogging
b) c) d)V 1
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Figure 1: a) Detached elastic clump of biofilm advected by the flow [1], scale bar = 20 microns. b) Experimental and numerical setup: elastic fibers transported by a uniform flow in a disordered array of obstacles. c) Time lapses from preliminary experimental data: fibers can either go through the periodic lattice (top) or clog (bottom).
