Orateur
Description
The pressure at the bottom of a container filled with granular material saturates [1], as the silo walls can support part of the grains' weight due to frictional interactions, a phenomenon known as the “Janssen Effect.”
We investigate this effect using ferromagnetic particles: when exposed to a magnetic field, these particles acquire a magnetic moment, leading to anisotropic magnetic interactions. We develop different experimental setups and Discrete Element Method (DEM) simulations [2], in both 3D and 2D.
We demonstrated recently that applying a magnetic field aligned with the granular column results in an even greater reduction of the pressure at the bottom of the container [3] compared to the classical Janssen Effect. Strikingly, beyond a critical magnetic field or a critical mass of grains, the apparent weight of the column can be completely canceled, rendering the column undetectable on the scale!
We focus on the approach of the “invisibility” threshold, examining the impact of the magnetic field intensity and the initial mass of grains. We also studied the influence of the proportion of ferromagnetic grains within the column: the pressure at the bottom of the column decreases only when the fraction of magnetic grains exceeds a threshold corresponding to the percolation of magnetic clusters [4].
[1] Janssen, H. A. Investigations of pressure of grain in silo. Vereins Eutscher Ingenieure Zeitschrift 1045-1049 (1895).
[2] J. Sautel, C.E. Lecomte, N. Taberlet, Particle size segregation in two-dimensional circular granular aggregates. Physical Review E, 103(2), 022901 (2021).
[3] L. Thorens, K.J. Måløy, M. Bourgoin, S. Santucci, Magnetic Janssen effect, Nature Comm., 12, 2486 (2021).
[4] L. Thorens, S. Rodriguez, N. Taberlet, M. Bourgoin, K.J. Måløy, S. Santucci, Hybrid Magnetic Janssen Effect Arising from Percolating Ferromagnetic Grain Networks, submitted 2026
| Do you submit an abstract for a talk or a poster? | poster |
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| If your abstract isn’t selected for a plenary talk, would you like to present it as a poster? | Yes |