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  • Gulliver seminar Jérôme Bonnet (CBS Montpellier)

    9 mars
    Lundi 16 mars 11:30-12:30 - Bibliothèque PCT - F3.04
  • Gulliver seminar, Stéphane Dorbolo (Université de Liège)

    11 février
    Lundi 9 mars 11:30-12:30 - Bibliothèque PCT - F3.04

    Leidenfrost is not only in a pan

    A droplet that is released on a hot pan is extremely mobile. Like the famous hovercraft, the droplet levitates on a gas cushion. In the case of the droplet, the gas is its own vapour. Indeed, the so-called Leidenfrost effect results of the liquid-gas transition. However, the temperature of the pan has to be much larger than the boiling temperature of the liquid the droplet is made because of the properties of the pan (nature and surface state). In this presentation, we would like first to extend the concept to other phase transitions. Then, we will test the classical Leidenfrost effect under high gravity conditions. As the roughness of the substrate is shown to be an issue to determine the Leidenfrost temperature, we will present the Leidenfrost effect on a liquid bath. In this case, the Leidenfrost temperature is very close to the boiling temperature of the droplet. Finally, the impact of droplet on hot liquid bath is the natural prolongation of this study. When the droplet manages to pierce the interface, it is time to discuss the existence of thermal antibubbles.

  • Gulliver seminar, François Hild (ENS Cachan)

    11 février
    Lundi 17 février 11:30-12:30 - Bibliothèque PCT - F3.04
  • Gulliver Seminar, Valérie Taly (Paris Descartes University)

    10 février
    Lundi 10 février 11:30-12:30 - Bibliothèque PCT - F3.04
  • Gulliver seminar, Anke Lindner (ESPCI Paris)

    27 janvier
    Lundi 27 janvier 11:30-12:30 - Bibliothèque PCT - F3.04

    Morphological transitions of flexible Brownian fibers in interaction with viscous flows

    In this presentation we discuss the individual dynamics of flexible and Brownian filaments under shear and compression. We use actin filaments as a model system and observe their dynamics in microfluidic flow geometries using fluorescent labelling techniques and microscopic tracking methods. Our experimental results are compared against Brownian dynamics simulations and theoretical models that describe actin filaments as thermal inextensible Euler–Bernoulli beams whose hydrodynamics follow slender-body theory. Theoretical modeling is used to explain different morphological transitions.

    Under shear we characterize successive transitions from tumbling to buckling and finally snake turns as a function of an elasto-viscous number. Under compression we reveal the formation of three dimensional helicoidal structures and characterize their formation.

    Finally, we attempt at linking the microscopic observations to the macroscopic suspension properties with preliminary measurements of the shear viscosity of dilute suspensions of actin filaments in microfluidic rheometers.

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