Discrete characterization tools for cohesive granular material

Granular flow is important scientifically as well as industrially. Often, cohesive forces between grains are the norm, rather than the exception; yet, the majority of research in granular materials has been directed at cohesionless materials. Due to the relatively large body of knowledge regarding cohesionless flows, gaining an understanding of the transition from cohesionless to cohesive behavior is of particular interest. In this work, we study systems where the predominant mode of cohesion is due to interstitial liquid (capillary cohesion). Both computations and experiments are used to explore a range of cohesive strengths (from cohesionless to cohesive). We propose two discrete characterization criteria, based on the physical picture of liquid-induced particle-level cohesion, which seem to work well in both static and flowing systems. Finally, we address limitations of this approach and discuss potential extensions to systems dominated by other modes of cohesion.