Flow and Jamming of Granular Suspensions in Foams

The drainage of particulate foams is studied under conditions where the particles are not trapped individually by constrictions of the interstitial pore space. The drainage velocity decreases continuously as the particle volume fraction $\phi_{p}$ increases. The suspensions jam - and therefore drainage stops - for values $\phi_{p}^{*}$ which reveal a strong effect of the particle size. In accounting for the particular geometry of the foam, we show that $\phi_{p}^{*}$ accounts for unusual confinement effects when the particles pack into the foam network. We model quantitatively the overall behavior of the suspension - from flow to jamming - by taking into account explicitly the divergence of its effective viscosity at $\phi_{p}^{*}$. Beyond the scope of drainage, the reported jamming transition is expected to have a deep significance for all aspects related to particulate foams, from aging to mechanical properties

Rotational modes in a 1D array of cylinders under shear stress

We study experimentally the frictional motion of a one-dimensional array of cylinders. Random experimental fluctuations of the confining stress induce a complex behaviour of each cylinder. We show that the mean motion of the particles can be described as a random superposition of well-ordered rotational steady state patterns