Ordered/disordered monodisperse dense granular flow down an inclined plane: dry versus wet media in the capillary bridge regime

A detailed study on similarities and differences of monodisperse dry and wet dense granular flow down on rough and smooth inclined planes was carried out by discrete element method simulations. Despite implementing a minimal model for capillary bridge cohesive force, all leading regimes of a granular flow, i.e. low-dissipation, high-dissipation, and oscillatory flow, can be developed in wet granular flow, similar to what we knew in the dry one. A smooth and rough based inclined planes as well as different inclination angels were used as parameters to create various flow regimes in dry and wet granular flow. In the oscillatory flow regime, the frequency of velocity profile variation is lower than that of the dry one. The velocity profile of the wet system in the low-dissipation flow regime exhibits an abrupt slope change at shear band bottom. As a measure of particle velocity fluctuations we have studied granular temperature in layers parallel to the inclined base. We found the temperature profile is increasing from the top to bottom, which means the shear band can be considered as a frozen region. By calculation of Radial Distribution Function (RDF) and using the adaptive Common Neighbor Analysis (a-CNA), the evolution of ordered/disordered structures in both dry and wet models is studied. In a wet system in the low-dissipation regime, the shear band exhibits frozen polycrystalline structure and in the bottom slice, in spite of having layered flow in the scale of one granule, we have a low fraction of crystallization. This study gives insightful key differences between wet and dry monodisperese granular flows, specifically the appearance of ordering and presence of crystalizations in different parts of high and low dissipation flow. Graphic abstract