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.
People |
ORCID iD |
Nathalie Maria Vriend (Principal Investigator) |
Publications
Ash M
(2014)
Two-dimensional radar imaging of flowing avalanches
in Cold Regions Science and Technology
Edwards A
(2016)
Size segregation in a granular bore
in Physical Review Fluids
Edwards A
(2016)
Size segregation in a granular bore
Keylock C
(2014)
Looking inside an avalanche using a novel radar system
in Geology Today
Vriend N
(2015)
Linear and nonlinear wave propagation in booming sand dunes
in Physics of Fluids
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 |