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Axisymmetric Granular Collapses -- 27/10/03
Herbert Huppert, (Institute of Theoretical Geophysics,University of Cambridge)
Gert Lube Gert Lube 1 ITG, CMS, DAMTP, University of Cambridge. 2 Department of Volcanology and Petrology, GEOMAR Kiel, Germany. 3 Department of Earth Sciences, University of Bristol. , (Geomar, Kiel, Germany)
Steve Sparks, (Dept of Earth Sciences, University of Bristol)
Mark Hallworth, (Institute of Theoretical Geophysics,University of Cambridge)
We will present investigations and movie sequences of a series of experiments in which initially vertical cylinders of different granular material collapse onto a horizontal base. We will describe the axisymmetric spreading in terms of three regimes dependent on the aspect ratio a=hi/ri, where the initial cylinder of material has radius ri and height hi. Almost all of the motion is quantitatively described by the same scaling relationships for the different granular materials, independent of any internal friction due to interactions between individual grains. Only at the end of the flow, when it comes to an abrupt halt, is intergranular friction important. The presentation will set up the framework to consider two-dimensional collapse down a channel or an inclined plane of different granular media into either air or water, a further study which will be discussed in a subsequent talk given by Gert Lube.