Streaming Sand Grains Help Define Essence of a Liquid
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| Audience/Grade: | College Freshman-Continuing Education |
| Discipline(s): |
Engineering Graphics and Visualization Engineering Mechanics Mechanical Engineering Nanotechnology Physics |
| Special Topic(s): | |
| Learning Resource Type: |
Reference - Visuals |
| Media Type: |
WWW |
| Author(s): |
John Royer |
| Description: | NSF funded project with insightful video of granular stream in free fall. "Water forms droplets because attractive interactions between molecules produce surface tension. If macroscopic objects—say, grains of sand—replace the molecules, the relative strength of this attraction would dramatically drop. What vestiges of liquid behavior remain in such ultra-low surface tension limit? Physicists seeking to answer this question have, for the first time, measured the nanoscale forces that cause droplet formation in a falling stream of tiny glass beads. John Royer, a graduate student in physics at the University of Chicago, devised a special apparatus for an $80,000 high-speed camera to image the rapidly changing behavior of the streaming sand, much as a skydiver might photograph a fellow jumper in free fall. Royer and his colleagues also measured grain-to-grain interactions directly with an atomic force microscope. They report in the journal Nature that the surface tension in this granular liquid is as much as 100,000 times smaller than that found in ordinary liquids. Citation: "High-Speed Tracking of Rupture and Clustering in Freely Falling Granular Streams," Nature, June 25, 2009, by John R. Royer, Daniel J. Evans, Loreto O. Gálvez, Quiti Guo, Eliot Kapit, Matthias E. Möbius, Scott R. Waitukaitis and Heinrich M. Jaeger, of the James Franck Institute and Department of Physics, University of Chicago" Image caption: Simulation of a granular stream in free fall, breaking into particle clusters like droplets in a stream of water falling from a faucet. As in ordinary liquids, weak attractive forces drive the clustering, but result here in a novel, ultra-low surface tension fluid |
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| Related Resources | |
| Keywords: | fluid dynamics doplets nanoscale granular streams |
| Usage Tip | |
| Related ABET Criteria: |
(b) Design and conduct experiments, analyze and interpret data |
| Use of Resource: |
Caption for high speed video that could be used for class demonstration: In this high-speed, high-resolution video, freely falling granular streams behave similarly to water flowing from a faucet. These granular streams behave like dense, cold fluids with ultra-low surface tension (cohesion between individual molecules). ?These experimental results open up new territory for which there currently is no theoretical framework,? John Royer and his co-authors.. Simulation performed using Itasca PFC3D 4.0 (http://www.itascacg.com/pfc3d/). Image rendered using POV-Ray 3.6 (http://www.povray.org). Helge F. Gruetjen, John R. Royer, Scott R. Waitukaitis, and Heinrich M. Jaege. |
| Difficulty: |
Medium |
| Interactivity Level: |
Medium |
| Version Info | |
| Publication Date: | June 2009 |
| Platform/Format: |
WWW |
| Cost: |
Free |
| Download URL: | http://news.uchicago.edu/news.php?asset_id=1643 |
| Metadata: |
IEEE LOM Record |
| Collection: |
NEEDS
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