Segregation in geophysical mass flows

Lead Research Organisation: University of Cambridge
Department Name: Applied Maths and Theoretical Physics

Abstract

Many people remember the churning debris flow finding its path downhill after the eruption of Mt. St. Helens in 1980 or reports about another snow avalanche that destroyed half a village and killed 20 people (Flateyri, Iceland, 1995). Perhaps less well-known is the pyroclastic flow that killed a group of scientists and journalists from a ``safe'' ridge (Mount Unzen, Japan, 1991) or the historic evidence and future predictions about underwater slides that cause tsunamis to travel many hundreds of kilometers, possibly even reaching the eastern coast of the USA (Cumbre Vieja volcano, Canary Islands). These geophysical flows are so powerful and destructive because of the continuous interaction between the fluid, solid and gas phases. Segregation within these geophysical mass flows is the driving force of inhomogeneity and results in enhanced mobility of the flow. Geophysical mass flows form a significant hazard for communities and directly influence the environment, infrastructure, economy and tourism of a region. A fundamental and thorough understanding of the influence of segregation on flow dynamics is therefore necessary to mitigate damage and loss of life. The continuous interaction between the fluid, solid and gas phases in geophysical mass flows creates a complicated material that is hard to characterize. As the bulk of the material is composed of particles with different sizes and densities, the material naturally segregates. This natural sieving of the components results in inhomogeneity between and within the phases and directly influences the flow characteristics. A back-to-basic problem involving segregation in geophysical mass flows is the transport of a dry granular material down an incline under the action of gravity. The fluid component is absent and the gas phase is air, but similar physical principles apply with regards to segregation of the solid components. The proposed work aims to understand the segregation in a dry granular material, providing the core physics for segregation in geophysical mass flows. We don't have to travel far to find segregation in our own kitchen. Shaking a box of cereal at home is a good illustration of the so-called 'Brazil nut effect' --- the larger particles end up at the surface while the smaller particles sink to the bottom. Intuitively one may think that this (size) sieving, or segregation, is simply due to the smaller particles falling into the holes between the larger particles. This explanation is qualitatively correct, but is has proved extremely difficult to construct a mathematical theory that can accurately predict the speed and degree of segregation. Segregation also occurs for same size but different density particles, as the denser particles move to the bottom of the mixture. Recent work on the development of phenomenological models encounters over and over again limitations on validation because of the meager amount of experimental data. Now is an excellent time to extend the amount of experimental data on segregation and use improved modern instrumentation to quantify the speed and degree of segregation within these flows. This research proposal describes a framework to perform laboratory experiments on dry granular mixtures of beads where the density, size and initial configuration are varied so as to obtain a large experimental database of segregation outcomes. The excellent experimental facilities and the expertise in numerical modeling of granular flows at DAMTP combined with the strong research background of the applicant will ensure the successful completion of the research project. The strength of the proposal is the combination of new cutting-edge laboratory experiments with simulations of segregation mechanisms in a numerical code. The multidisciplinary nature of this proposal is complemented by a theoretical modeling effort and an experimental field component resulting in reality-based models that may be used by scientists and policymakers alike.

Publications

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Ash M (2014) Two-dimensional radar imaging of flowing avalanches in Cold Regions Science and Technology

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Edwards A (2016) Size segregation in a granular bore in Physical Review Fluids

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Keylock C (2014) Looking inside an avalanche using a novel radar system in Geology Today

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Vriend N (2013) High-resolution radar measurements of snow avalanches in Geophysical Research Letters

 
Description NERC Geophysical Equipment Facility grant
Amount 2,400 ج.م.‏ (EGP)
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 12/2014 
End 02/2015
 
Description Royal Society Dorothy Hodgkin Fellowship
Amount £650,000 (GBP)
Funding ID RS 
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 01/2014 
End 12/2018
 
Description Royal Society Research Grant
Amount £131,437 (GBP)
Organisation The Royal Society 
Sector Charity/Non Profit
Country United Kingdom
Start 09/2015 
End 09/2018
 
Description University of Cambridge Early Career Support Scheme
Amount £50,000 (GBP)
Organisation University of Cambridge 
Sector Academic/University
Country United Kingdom
Start 01/2016 
End 03/2017
 
Description Collaboration with JT Thomas, BFW Innsbruck, Austria 
Organisation Medical University of Innsbruck
Country Austria 
Sector Academic/University 
PI Contribution Collaboration with JT Thomas, BFW Innsbruck, Austria
Start Year 2014
 
Description Collaboration with Prof. Karen Daniels, North Carolina State University, Raleigh, USA 
Organisation North Carolina State University
Country United States 
Sector Academic/University 
PI Contribution Not available yet
Collaborator Contribution Hosting a research student for a month to provide training on specialized techniques.
Impact Not yet available.
Start Year 2015
 
Description Collaboration with Prof. Michel Louge, Cornell University, Ithaca 
Organisation Cornell University
Department Sibley School of Mechanical and Aerospace Engineering
Country United States 
Sector Academic/University 
PI Contribution Two combined field-trips to the Qatari desert to investigate mobile barchan sand dunes.
Collaborator Contribution Logistical support and partly contribution in travel costs.
Impact "The fine-grained structure of avalanches and sand dunes" ? Two-phase continuum models for geophysical particle-fluid flows, Max-Planck Institute Dresden, Germany, March 14 - 18, 2016. "Marching desert dunes avalanche, bury and disappear!" ? Lates Event, Science Museum London, London, UK, Jun 24th, 2015. Nathalie Vriend Page 4 of 7 ? Twilight Science at the Summer Science Exhibition, Royal Society, London, UK, June 29th, 2015.
Start Year 2014
 
Description "X-ray Yellowstone" 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Interview & item on snow avalanches, Discovery Channel TV, Dec 24, 2012

Interview with me as an expert on snow avalanches, contributing to the documentary.
Year(s) Of Engagement Activity 2012
 
Description BBC2: Nature's Weirdest Events 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Media (as a channel to the public)
Results and Impact Contributor and interviewed for an episode for BBC's Nature's Weirdest Events, focussing on my sand dunes work.
Year(s) Of Engagement Activity 2014,2015
 
Description Lates Event, Science Museum London, London, UK, Jun 24th, 2015. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Invited lecture at the "Lates Event" at the Science Museum in London, UK.
Year(s) Of Engagement Activity 2015
 
Description Media attention from scientific publication 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Press release & news coverage in Scientific American, Phys.org, Discovery News, The Weather Channel, Fox News, Smithsonian.com, SpaceDaily, livescience.com, the Examiner, International Business Times, Gizmodo, Discovery Canada & international newspapers following from our Phys. of Fluids article, Oct. 2015
Year(s) Of Engagement Activity 2015
 
Description Royal Society Summer Science Exhibition 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? Yes
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact A public display at the 2012 Royal Society Summer Science Exhibition

Dr. Nathalie Vriend, a NERC Research Fellow in DAMTP organized a popular display on "Setting a Speed Trap for an Avalanche".

The exhibition was well-attended with visitor's numbers exceeding 13.000. During the week the visitors mainly consisted of hig
Year(s) Of Engagement Activity 2012
 
Description Twilight Science at the Summer Science Exhibition, Royal Society, London, UK, June 29th, 2015. 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Invited lecture at the Royal Society Summer Science Exhibition, London, UK
Year(s) Of Engagement Activity 2015