| Fluctuations in the local volume fraction in granular materials have been observed to decrease as the volume fraction of system increases. For a dense, driven 2D bidisperse granular material, we examine the generality of this observation by measuring the role of boundary condition and inter-particle friction on the volume fraction statistics. Using a radical Voronoi tessellation, we measure the local volume fraction, φ, for many configurations and find a universal relationship between the variance and mean of φ. We find that a modification of the granocentric model, recently proposed by Clusel et. al. for jammed 3D granular materials, is able to accurately predict the observed relationship. |
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