Relevance of system size to the steady-state properties of tapped granular systems

Abstract

We investigate the steady-state packing fraction phi and force moment tensor of quasi-two-dimensional granular columns subjected to tapping. Systems of different height h and width L are considered. We find that<br />phi and , which describe the macroscopic state of the system, are insensitive to L for L > 50d (with d the grain diameter). However, results for granular columns of different heights cannot be conciliated. This suggests that comparison between results of different laboratories on this type of experiments can be done only for systems of same height. We show that a parameter epsilon = 1 + (A omega)2 /(2gh), with A and omega the amplitude and frequency of the tap and g the acceleration of gravity, can be defined to characterize the tap intensity. This parameter is based on the effective flight of the granular bed, which takes into account the h dependency. When phi is plotted as a function of epsilon, the data collapses for systems of different h. However, this parameter alone is unable to determine the steady state to be reached since different can be observed for a given epsilon if different column heights are considered.<br /><br />