Statistics of a two-dimensional immersed granular gas magnetically forced in volume

Jean-Baptiste Gorce and Eric Falcon

Université Paris Cité, MSC Laboratory, UMR 7057 CNRS, F-75 013 Paris, France



Reference: Physical Review E 107, 034903 (2023)   

URL: https://journals.aps.org/pre/abstract/10.1103/PhysRevE.107.034903
DOI: https://doi.org/10.1103/PhysRevE.107.034903


Abstract:
We present an experimental study of the dynamics of a set of magnets within a fluid in which a remote torque applied by a vertical oscillating magnetic field transfers angular momentum to individual magnets. This system differs from previous experimental studies of granular gas where the energy is injected by vibrating the boundaries. Here, we do not observe any cluster formation, orientational correlation and equipartition of the energy. The magnets’ linear velocity distributions are stretched exponentials, similar to three-dimensional boundary-forced dry granular gas systems, but the exponent does not depend on the number of magnets. The value of the exponent of the stretched exponential distributions is close to the value of 3/2 previously derived theoretically. Our results also show that the conversion rate of angular momentum into linear momentum during the collisions controls the dynamics of this homogenously-forced granular gas. We report the differences between this homogeneously-forced granular gas, ideal gas, and nonequilibrium boundary-forced dissipative granular gas.

PDF

Movie illustrating the motions of the magnets immersed in water within the quasi-2D container.
The magnets' trajectories (red) are shown for 2 s (slow down 5 times).
The number of magnets is equal to N=20. The frequency and amplitude of the magnetic field are 50 Hz and 162 G, respectively.
The window size is equal to 11 x 6 cm2.




 
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