Defence of thesis: Louison Thorens

Louison Thorens will defend his thesis Unstable drainage of frictional fluids and magnetic control of the mechanical behavior of confined granular media for the degree of Philosophiae Doctor.

Time and place: Nov. 17, 2021 1:15 PM, Zoom/Kelvin (V317), Fysikkbygningen

The PhD defence and trial lecture are partially digital and streamed using Zoom.  The chair of the defence will moderate the disputation.

Ex auditorio questions: the chair of the defence will invite the audience to ask ex auditorio questions

Trial lecture:
Time and place: Nov 17, 2021 10:15 AM, Kelvin and Zoom
Title: “Active granular matter

Main research findings

The transport of immersed grains in confined media relevant for many industrial and natural situations highlights the complex interaction between capillary and granular stress.
In this thesis, we have studied the triggering of a bulldozing instability, leading to the formation of granular plugs during the slow drainage of a frictional fluid, mixture of a liquid and grains sedimented in a capillary. We could reveal a new unstable regime leading to the periodic formation of dunes. Furthermore, we have developed an original method to control the frictional interactions at the origin of this bulldozing instability, by using ferromagnetic particles: submitted to a magnetic field, they acquire a magnetic moment, leading to tunable interactions of pairs of magnetic dipoles. We demonstrated the emergence of a radial force along the walls of the container, whose amplitude and direction are determined by the applied magnetic field. This “magnetic Janssen effect” allows to control the apparent mass of the granular column, paving the way towards the design of granular meta-materials, whose mechanical (un)jamming properties can be remotely controlled or even programmed.

Image may contain: Rectangle, Line, Slope, Parallel, Wood.

Adjudication Committee

  • Professor Eric Clément, ESPCI–PSL–Sorbonne University, France
  • Associate Professor Axelle Amon, University of Rennes, France
  • Professor Dag Kristian Dysthe, University of Oslo, Norway
  • Associate Professor Nicolas Taberlet, ENS de Lyon, France
  • Professor Pascale Aussillous, Aix-Marseille University, France


  • Professor Knut Jørgen Måløy, Department of Physics – Porelab / UiO, Norway
  • Professor Eirik Grude Flekkøy, Department of Physics – Porelab / UiO, Norway
  • Dr. Mickaël Bourgoin, Laboratoire de Physique / ENS de Lyon, France
  • Dr. Stéphane Santucci, Laboratoire de Physique / ENS de Lyon, France

Chair of defence

  • Professor Andreas Görgen, Department of Physics, University of Oslo, Norway

Contact information to Department: Line Trosterud Resvold

More information here: