RESOURCES: Totally Granular

Science  26 Jul 2002:
Vol. 297, Issue 5581, pp. 483
DOI: 10.1126/science.297.5581.483b

Much of what spews from the maw of a volcano, such as clouds of ash or streams of sizzling muck, qualifies as a granular flow, a mixture of fine particles swept along by a fluid such as water or air.

The Web site Granular Volcano Group provides an introduction to the physics of these mixtures written by Sébastien Dartevelle, a Ph.D. student at Michigan Technological University in Houghton. The details of granular flow get hairy because the fluid and the particles are in different phases, so the equation-laden site is not for the math-phobic or physics-averse. Sections cover topics such as viscosity within a stream of particles, friction between grains, and models of granular flows. You can also watch movies of supercomputer simulations of various kinds of gas clouds and debris flows.

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