Inertial effects in just-saturated axisymmetric column collapses

Webb, William; Heron, Charles; Turnbull, Barbara

Abstract

This work introduces a scaling analysis of sub-aerial axisymmetric column collapses of glass beads and Newtonian glycerol-water solutions mimicking some of the behaviours of debris flows. The beads were in a size range where their inertia partly decouples their collapse behaviour from the water column. Experiments explored a range of viscous, surface tension and particle inertia effects through systematic variation of particle size and fluid viscosity. Crucially a geotechnical centrifuge was used to access elevated effective gravitational accelerations driving the collapse, allowing field-scale viscous and surface tension effects to be replicated. Temporal pore pressure and run out front position evolution data was extracted using a pressure transducer and high speed imaging, respectively. A least-squares fitted scale analysis demonstrated that all characteristic dimensionless quantities of the acceleration phase could be described as a function of the column-scale Bond number Bo, the Capillary number Ca, the system size r∗, and the grain-fluid density ratio ρ∗. This analysis demonstrated that collapses as characterised by pore pressure evolution and front positions were controlled by the ratio of Bo/Ca. This indicates that grain-scale surface tension effects are negligible in such inertial column collapses where they may dominate laboratory-scale granular-fluid flow behaviour where geometric similarity between grain and system size is preserved. Graphical abstract:

Citation

Webb, W., Heron, C., & Turnbull, B. (2023). Inertial effects in just-saturated axisymmetric column collapses. Granular Matter, 25(2), Article 40. https://doi.org/10.1007/s10035-023-01326-x

• Journal Article Type: Article
• Acceptance Date: Apr 1, 2023
• Online Publication Date: May 3, 2023
• Publication Date: 2023-05
• Deposit Date: May 10, 2023
• Publicly Available Date: May 10, 2023
• Journal: Granular Matter
• Print ISSN: 1434-5021
• Electronic ISSN: 1434-7636
• Publisher: Springer Science and Business Media LLC
• Peer Reviewed: Peer Reviewed
• Volume: 25
• Issue: 2
• Article Number: 40
• DOI: https://doi.org/10.1007/s10035-023-01326-x
• Keywords: Granular collapse, Inertial regime, Just-saturated, Scaling analysis, Centrifuge modelling
• Public URL: https://nottingham-repository.worktribe.com/output/20553550
• Publisher URL: https://link.springer.com/article/10.1007/s10035-023-01326-x
• Additional Information: Received: 4 May 2022; Accepted: 1 April 2023; First Online: 3 May 2023; : ; : The authors declare that they have no conflict of interest.; : The raw video files for all completed tests are available at ExternalRef removed.