Fluidization of granular media wetted by liquid ${}^4$He

Abstract

We explore experimentally the fluidization of vertically agitated PMMA spheres wetted by liquid ${}^4$He. By controlling the temperature around the $\lambda$ point we change the properties of the wetting liquid from a normal fluid (helium I) to a superfluid (helium II). For wetting by helium I, the critical acceleration for fluidization (${\Gamma }_c$) shows a steep increase close to the saturation of the vapor pressure in the sample cell. For helium II wetting, ${\Gamma }_c$ starts to increase at about 75% saturation, indicating that capillary bridges are enhanced by the superflow of unsaturated helium film. Above saturation, ${\Gamma }_c$ enters a plateau regime where the capillary force between particles is independent of the bridge volume. The plateau value is found to vary with temperature and shows a peak at 2.1 K, which we attribute to the influence of the specific heat of liquid helium.

4 pages, 3 figures, Accepted by Phys. Rev. E as a rapid communication

References in corpus (3)

• How Sandcastles Fall
• Maximum Angle of Stability of a Wet Granular Pile
• Two-dimensional melting far from equilibrium in a granular monolayer

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