Granular research in extremes: from sand dunes in the desert to snow avalanches in the mountains


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• Nathalie Vriend (University of Cambridge)
• Tuesday 02 February 2010, 13:00-14:00
• MR14, DAMTP, Pav. F.

If you have a question about this talk, please contact Dr Geoffroy Lesur.

The transport of a granular material down an incline under the action of gravity is an example of a geophysical mass flow. These geophysical mass flows occur in a variety of forms on Earth, ranging from churning debris flow (Mt. St. Helens in 1980) to snow avalanches (Flateyri, Iceland, 1995) and from pyroclastic flows (Mount Unzen, Japan, 1991) to underwater slides causing tsunamis (Cumbre Vieja volcano, Canary Islands).

In this presentation I will highlight research done during my PhD at the California Institute of Technology, USA on Booming Sand Dunes and provide a sneak-peak of my postdoctoral research at the University of Cambridge on Snow Avalanches. 
“Booming” sand dunes are able to produce a persistent, low-frequency sound that resembles a pure note from a music instrument. The sound has a dominant audible frequency (70 – 105 Hz) and several higher harmonics that may be heard from distances far away. A natural or induced avalanche from a slip face of the booming dune triggers an emission that may last for several minutes. Quantitative field research at dunes found in the Mojave Desert and Death Valley National Park in California, USA provides experimental data.

Snow avalanches form a significant hazard for communities and directly influence the environment, infrastructure, economy and tourism of a region. The knowledge on the fluid dynamics of these unpredictable avalanches is poor because of limitations on measuring the internal structure of a large-scale avalanche. Different flow regimes (dense core, saltation and suspension layer) are apparent with orders of magnitude difference in density. A collaborative (Leeds, UCL ) new effort, spear-headed by Dr. Jim McElwaine at Cambridge, measures the velocity distribution of the dense core with an advanced Doppler Radar System. Field experiments are scheduled this winter at Vallée de la Sionne in Switzerland.

This talk is part of the DAMTP Astro Lunch series.

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