[ghsc-seminars] GHSC Seminar *HYBRID* - Nathalie Vriend, UC Boulder, January 24, 2023

[Llenos, Andrea L]

Granular and Photoelastic Avalanches

Speaker: Nathalie Vriend
                Department of Mechanical Engineering
                University of Colorado Boulder
Location: HYBRID (online and in-person at 1711 Illinois St, Golden, CO, Rm 204)
                *Non-USGS visitors are welcome! Please bring a photo ID and plan to arrive ~15 min early to allow time to go through building security.*
Date/Time: Tuesday, January 24, 2023 10-11am MST

Abstract: Flowing granular materials arise everywhere around us, in industry from pharmaceutical processes to bulk good transport lines, and in nature from snow avalanches to captivating dune fields.
In landslides, we have an interesting interplay between microscale (grain-grain contacts) and macroscale processes (continuum behavior). In order to understand critical macroscale processes such as stability of a slope, creep and failure, we need to be able to visualize and characterize the microscale interactions.

In this talk, I will introduce a laboratory technique called photoelasticity to visualize grain-grain contacts in time and space. Collisions between grains create a fascinating network of so-called force chains, which are responsible for the inhomogeneous distribution of stresses in a granular medium. We discover stress distributions in 2D granular avalanches, visualized with bespoke, superior-quality birefringent photoelastic particles. This technique gives us for the first time access to the full velocity, density and stress fields inside of a dynamic avalanche, and allows us to experimentally validate granular rheological models.

Bio: Associate Professor Nathalie Vriend joined the University of Colorado Boulder in 2022. Prior to CU Boulder, she spend a 12-year period in the United Kingdom at the University of Cambridge. After a short postdoctoral position (2010 – 2011) and holding a competitive personal postdoctoral fellowship (2011 – 2013) in the Department of Applied Mathematics and Theoretical Physics (DAMTP), she started her own research group. Between 2014 and 2022, Nathalie has been group leader and Royal Society Research Fellow, first as a Dorothy Hodgkin Research Fellow in DAMTP and from 2019 onwards as a University Research Fellow at the BP Institute, both at the University of Cambridge.

Dr. Vriend earned her ingenieurs (B.Sc. + M.Sc.) degree in Mechanical Engineering (2004) from the University of Twente, The Netherlands and her M.Sc. (2005, in Aeronautics) and Ph.D. degree (2010, in Mechanical Engineering and Geophysics) from the California Institute of Technology, USA.

Dr. Vriend leads the Granular Flow Laboratory at CU Boulder. She is an expert in performing detailed laboratory experiments and targeted field work involving particulate flows such as sand and snow. In addition, she also employs numerical simulations and theoretical modelling to complement observations, often in collaboration with scientists from multidisciplinary fields. She has active projects in granular rheology and avalanching, and dune structure and migration. In the past she worked on the dynamics of real snow avalanches, singing sand dunes, silo honking, and seismic wave propagation.

[cid:b6cb02c6-99e9-4b81-a7d6-ec98ac4b2252]


For questions, comments, or speaker suggestions, please contact the GHSC Seminar Committee: Andrea Llenos <allenos at usgs.gov>, Benjamin Murphy <bmurphy at usgs.gov>, Lauren Schaefer <lschaefer at usgs.gov>


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