Sedimentation of a suspension of paramagnetic particles in an external magnetic field

Vessaire, Jérémy; Plihon, Nicolas; Volk, Romain; Bourgoin, Mickaël

doi:10.1103/physreve.102.023101

Cited by 5 publications

(2 citation statements)

References 23 publications

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“…The whole setup is placed between two coils mounted in a Helmholtz configuration, generating a uniform magnetic field B in the vertical direction as shown in figure 1b. To quantify the effect of the magnetic interaction, we can consider the dimensionless number Ψ, (sometimes referred as a magnetic Bond number [15,16]), which compares magnetic pair interaction and gravity, Ψ = (χ m B) 2 /(µ 0 aρg) where χ m is the magnetic susceptibility of the beads equal to 3 in the case of a random close packing [17], µ 0 is the magnetic permeability of vacuum, a the beads are poured inside a tube using a hopper until we reach the desired mass m0, 2. the packing is at rest and the hopper is removed, 3. downward movement of the vertical translation stage, the mass measurement corresponds to the mean plateau value.…”

Section: Methodsmentioning

confidence: 99%

Taming the Janssen effect

et al. 2021

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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.

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Section: Methodsmentioning

confidence: 99%

Taming the Janssen effect

et al. 2021

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“…water), subjected to a weak external magnetic induction environment (thus no liquid magnetisation occurs). Some studies explored the effects of a homogeneous magnetic induction on one or more particles in non-magnetic fluids [24][25][26][27][28] . In these studies, the main focus was exploring the role of particle/particle interactions on their coupling with the fluid, using a homogeneous magnetic field as a way to tune interactions between particles.…”

Section: Introductionmentioning

confidence: 99%

Tuning particle settling in fluids with magnetic fields

Cabrera-Booman,

Plihon,

Cal

et al. 2024

Exp Fluids

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A magnetic field (MF) is generated to modify gravity in a laboratory. The MF produces a vertical force that counteracts the gravitational field on a magnetic sphere. The perpendicular spin of particles is blocked, thus allowing spin solely around the direction of the MF. The settling of spherical magnets in a quiescent flow with a particle density of 8200 kg/m 3 and Galileo number (Ga) in the range [100, 280] was studied experimentally. The results obtained by varying Ga via gravity modification to those obtained with nonmagnetic spheres where Ga is modified by varying viscosity are compared. Findings showed that there is no significant difference in the trajectory angle between magnetic and non-magnetic cases, suggesting that the method for compensating gravity does not produce any spurious effect and that particle spinning has no significant effect on this aspect of the dynamics. Subtle differences in trajectory planarity were observed hinting at a possible dependence on particle spin. Results prove the validity of the method introduced here to change the gravitational strength on particles in fluids.

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Magnetic Janssen effect

et al. 2021

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A pile of grains, even when at rest in a silo, can display fascinating properties. One of the most celebrated is the Janssen effect, named after the pioneering engineer who explained the pressure saturation at the bottom of a container filled with corn. This surprising behavior arises because of frictional interactions between the grains through a disordered network of contacts, and the vessel lateral walls, which partially support the weight of the column, decreasing its apparent mass. Here, we demonstrate control over frictional interactions using ferromagnetic grains and an external magnetic field. We show that the anisotropic pairwise interactions between magnetized grains result in a radial force along the walls, whose amplitude and direction is fully determined by the applied magnetic field. Such magnetic Janssen effect allows for the fine tuning of the granular column apparent mass. Our findings pave the way towards the design of functional jammed materials in confined geometries, via a further control of both their static and dynamic properties.

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Sedimentation of a suspension of paramagnetic particles in an external magnetic field

Cited by 5 publications

References 23 publications

Taming the Janssen effect

Taming the Janssen effect

Tuning particle settling in fluids with magnetic fields

Magnetic Janssen effect

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