Fluid-particle interaction in geophysical flows: debris flow

Paleo Cageao, Paloma (2014) Fluid-particle interaction in geophysical flows: debris flow. PhD thesis, University of Nottingham.

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Small scale laboratory experiments were conducted to study the dynamic mor- phology and rheological behaviour of fluid-particle mixtures, such as snout-body architecture, levee formation, deposition and particle segregation effects. Debris flows consist of an agitated mixture of rock and sediment saturated with water. They are mobilized under the influence of gravity from hill slopes and channels and can reach long run-out distance and have extremely destructive power. Better understanding of the mechanisms that govern these flows is required to assess and mitigate the hazard of debris flows and similar geophysical flows. Debris flow models are required to accurately deal with evolving behaviours in space and time, to be able to predict flow height, velocity profiles and run-out distances and shapes. The evolution of laboratory debris flows, both dry glass beads and mixtures with water or glycerol, released from behind a lock gate to flow down an inclined flume, was observed through the channel side wall and captured with high speed video and PIV analysis to provide velocity profiles through out the flow depth. Pore pressure and the normal and shear stress at the base of the flow were also measured.

Distinct regions were characterized by the non-fluctuating region and the in- termittent granular cloud surrounding the flows. The extent of these regions was shown to be related to flow properties. The separation of these two regions allowed the systematic definition of bulk flow characteristics such as characteristic height and flow front position. Laboratory flows showed variations in morphology and rheological characteristics under the influence of particle size, roughness element diameter, interstitial fluid viscosity and solid volume fraction. Mono-dispersed and poly-dispersed components mixed with liquids without fine sediments, reveal a head and body structure and an appearance similar to the classic anatomy of real debris flows. Unsaturated fronts were observed in mono-dispersed flows, suggesting that particle segregation is not the only mechanism.

A numerical simulation of laboratory debris flows using the computer model RAMMS (RApid Mass Movements Simulation) was tested with dry laboratory flows, showing close similarity to calculated mean velocities.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Turnbull, A.
Keywords: Debris avalanches, Fluid dynamics, Dynamic morphology, Rheological behaviour, RApid Mass Movements Simulation
Subjects: Q Science > QC Physics
Faculties/Schools: UK Campuses > Faculty of Engineering
UK Campuses > Faculty of Engineering > Department of Civil Engineering
Item ID: 27808
Depositing User: Paleo Cageao, Paloma
Date Deposited: 02 Mar 2015 08:54
Last Modified: 14 Sep 2016 15:32
URI: http://eprints.nottingham.ac.uk/id/eprint/27808

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