Heterogeneous structure of granular aggregates with capillary interactions

Abstract

We investigate the spatial structure of cohesive granular matter with spheres floating at an air-liquid interface that form disordered close packings with pores in between. The interface is slowly lowered in a conical container to uniformly compress and study the system as a function of area fraction $\phi$. We find that the free area distributions associated with Voronoi cells show significant exponential tails indicating greater heterogeneity compared with random distributions at low $\phi$ with a crossover towards a $\Gamma$-distribution as $\phi$ is increased. Further, we find significant short range order as measured by the radial correlation function and the orientational order parameter even at low and intermediate $\phi$, which is absent when particles interact only sterically.