Abstract
Sub-aerial (dry) and submerged dense granular collapses are studied by means of a three-phase unresolved computational fluid dynamics-discrete element method (CFD-DEM) numerical model. Physical experiments are also performed to provide data for validation and further analysis. Validations show good compatibility between the numerical and experimental results. Collapse mechanism as well as post-collapse morphological parameters, such as granular surface profile and runout distance, are analyzed. The spatiotemporal variation of solid volume fraction is also investigated. The effect granular column aspect ratio is studied and found to be a key factor in granular morphology for both submerged and dry conditions. The volume fraction analysis evolution shows an expansion and re-compaction trend, correlated with the granular movement.
Highlights
Granular collapses are characterized by the rapid movement of granular material, driven by gravity
The coupling of these two methods is based on an unresolved computational fluid dynamics-discrete element method (CFD-discrete element method (DEM)) coupling to reduce the computational time
To evaluate the capability of the DEM model, in the absence of the computation fluid dynamics (CFD) model, it is applied to the dry granular collapse cases D1 and D2
Summary
Granular collapses are characterized by the rapid movement of granular material, driven by gravity. They are widely encountered in various geophysical and engineering processes, for example, in the submarine and sub-aerial landslides, debris flows, and river back failures. Understanding the behavior of the granular collapses is crucial for the prediction and mitigation of rated natural disasters with destructive consequences. Granular collapses present very complex mechanics as they often include all regimes of granular flows, i.e., quasi-static, dense flow, and kinetic (or gaseous) regimes in the same setting [1]. The situation is still more complex when the granular collapses are submerged. The interaction with an ambient viscous and dense fluid like water, in presence of the free surface, creates a complex 3-phase system. The fluid inertia, viscosity, and pore pressure can dramatically affect the granular behaviour [1,2,3,4]
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