EPJ Web Conf.
Volume 249, 2021Powders & Grains 2021 – 9th International Conference on Micromechanics on Granular Media
|Number of page(s)||4|
|Section||Cohesive Granular Materials|
|Published online||07 June 2021|
Taming the Janssen effect
Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS, Laboratoire de Physique, F-69342 Lyon, France
2 PoreLab, The Njord Centre, Department of Physics, University of Oslo, P. O. Box 1048 Blindern, N-0316 Oslo, Norway
3 Lavrentyev Institute of Hydrodynamics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
* e-mail: email@example.com
Published online: 7 June 2021
We investigate both experimentally and theoretically the apparent mass of a ferromagnetic granular assembly filling a cylindrical container and submitted to a magnetic field B, aligned vertically along the silo. We show that the mass of the ferromagnetic granular column depends strongly on the applied magnetic field. Notably, our measurements deviate strongly from the exponential saturation of the measured mass as a function of the true mass of the grain packing, as predicted by Janssen [H.A. Janssen, Vereins Eutscher Ingenieure Zeitschrift, 1045 (1895)]. In particular, the measured mass of tall columns decreases systematically as the amplitude of the magnetic field increases. We rationalize our experimental findings by considering the induced magnetic dipole-dipole interactions within the whole packing. We show the emergence of a global magnetic radial force along the walls of the silos, fully determined by the external magnetic field. The resulting tunable frictional interactions allows a full control of the effective mass of the ferromagnetic granular column.
A video is available at https://doi.org/10.48448/2292-nz67
© The Authors, published by EDP Sciences, 2021
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