APS -70th Annual Meeting of the APS Division of Fluid Dynamics- Event - Dynamics and pattern transition in a two-dimensional vibrofluidized granular bed

摘要

Experiments are conducted in a two-dimensional monolayer vibrofluidized bed ofglass beads, with an aim to study the dynamics and the transition scenario indifferent patterned states. At small shaking accelerations ($Gamma=Aomega^2/g<1$, where $A$ and $omega= 2pi f $ are the amplitude and angular frequency of shaking and $g$ is the gravitational acceleration),the particles remain attached to the base of the vibrating container; this is known asthe solid bed (SB). With increasing $Gamma$ (at large enough shaking amplitude $A/d$) and/orwith increasing $A/d$ (at large enough $Gamma$), the sequence of transitions/bifurcationsunfolds as follows: SB (“solid bed”) to BB (“bouncing bed”) to LS (“Leidenfrost state”)to “2-roll convection” to “1-roll convection” and finally to a gas-like state. For a givenlength of the container, the coarsening of multiple convection rolls leading to thegenesis of a “single-roll” structure (dubbed the "multiroll transition") and its subsequenttransition to a granular gas are two findings of this work. We show that the criticalshaking intensity $Gamma_{BB}^{LS}$ for the $BB ightarrow LS$ transition has a power-law dependence on the particle loading ($F$) and the shaking amplitude ($A/d$).