PhD defense of Alice Pelosse

Sep 25, 2023 | Soutenance

Friday, September 29th, 10h00, Pierre-Gilles de Gennes amphitheater Level -1, Condorcet Building.

PhD defense of Alice Pelosse
Capillary flows of granular suspensions.

supervised by Elisabeth Guazzelli and Matthieu Roché

 

Abstract:
This work focuses on the capillary flow of granular suspensions. Suspensions, heterogeneous mixtures of particles in a fluid, are ubiquitous in our environment and in the industry (blood, avalanches, cosmetics, cement). Granular suspensions are used when particle agitation is negligible. Unlike most studies dealing with large volumes of surface-air suspensions, my research focuses on millimeter flows of suspensions coupled to a dynamic interface. These flows are then called capillary flows because they are dominated by capillary forces at the interface. The suspended particles then interact with an interface that confines them more or less according to their size. My approach, based on experience, is deepened by theoretical reflections on the key ingredients of modeling these systems.

    First, I studied how these suspensions spread over a surface and showed that particles can be used as probes to understand how energy dissipation occurs in the liquid by cleverly playing with their size. Thus, my work enriches our knowledge of granular suspensions, but also of dynamic anchoring in general. In particular, I have shown experimentally that the classical laws of Tanner and Cox-Voinov still hold provided one uses effective viscosities that can depend on different parameters.
    My second project investigates the effect of particles in gravitationally unstable thin films. This Rayleigh-Taylor instability selects a more unstable hexagonal pattern for a continuous fluid characterized by wavelength and growth time. With the addition of particles, the instability is found to exhibit two regimes: for small particles, the instability differs from the simple fluid only in its growth rate. For larger particles, the instability is inhibited. In addition to deepening our understanding these phenomena, these results pave the way for stabilizing thin films by adding particles.
 

Author: Alice Pelosse