Two-dimensional sub-aerial, submerged, and transitional granular slides

Abstract

The slide of granular material in nature and engineering can happen under air (subaerial), under a liquidlike water (submerged), or a transition between these two regimes, where a subaerial slide enters a liquid and becomes submerged. Here, we experimentally investigate these three slide regimes (i.e., subaerial, submerged, and transitional) in two dimensions, for various slope angles, material types, and bed roughness. The goal is to shed light on the complex morphodynamics and flow structure of these granular flows and also to provide comprehensive benchmarks for the validation and parametrization of the numerical models. The slide regime is found to be a major controller of the granular morphodynamics (e.g., shape evolution and internal flow structure). The time history of the runout distance for the subaerial and submerged cases present a similar three-phase trend (with acceleration, steady flow, and deceleration phases) tough with different spatiotemporal scales. Compared to the subaerial cases, the submerged cases show longer runout time and shorter final runout distances. The transitional trends, however, show additional deceleration and reacceleration. The observations suggest that the impact of slide angle, material type, and bed roughness on the morphodynamics is less significant where the material interacts with water. Flow structure, extracted using a granular particle image velocimetry technique, shows a relatively power-law velocity profile for the subaerial condition and strong circulations for the submerged condition. An unsteady theoretical model based on the µ(I) rheology is developed and is shown to be effective in the prediction of the average velocity of the granular mass.

The mechanics of landslide mobility with erosion

“…These problem-specific solutions provide important insights into the full behavior of the system. A physically meaningful exact solution explains the true and entire nature of the problem associated with the model equation [51][52][53]66 . However, numerical solutions are always subject to questions as such solutions are based on some assumptions and applied approximations that may not follow the laws of nature.…”

“…Physics-based models and numerical simulations may overcome these limitations and facilitate a more complete understanding by investigating much wider aspects of the flow parameters, erosion, mobility, and deposition. Similarly, exact, analytical solutions [50][51][52][53] can provide important insights into the complex flow behaviors and their consequences.…”

The Mechanics of Landslide Mobility with Erosion

“…These problem-specific solutions provide important insights into the full behavior of the system. A physically meaningful exact solution explains the true and entire nature of the problem associated with the model equation (Pudasaini, 2011;Faug, 2015;Pudasaini et al, 2018;Pilvar et al, 2019). However, numerical solutions are always subject to questions as such solutions are based on some assumptions and applied approximations that may not follow the laws of nature.…”

“…Physics-based models and numerical simulations may overcome these limitations and facilitate a more complete understanding by investigating much wider aspects of the flow parameters, erosion, mobility and deposition. Similarly, exact, analytical solutions (Faug et al, 2010;Pudasaini, 2011;Pudasaini et al, 2018;Pilvar et al, 2019) can provide important insights into the complex flow behaviors and their consequences.…”

Fluid-driven granular dynamics through a consistent multi-resolution particle method

“…Many hydro-environmental and geotechnical problems involve the multiphase flow of granular material, like sediment, immersed in a fluid, like water (Figure 1-a). In such multiphysics systems, the granular phase demonstrates dynamic solid-and fluid-like behaviors induced by gravity and the ambient fluid flow (e.g., in the cases of submarine landslides [1,2,3,4,5] and fluvial and coastal sediment transport [6,7,8]). Particularly, rapid shearing flows over granular beds cause large interfacial deformations leading to the erosion, suspension, and deposition of grains [9].…”