Granular Avalanches
Granular avalanches are abundant in the natural environment on a very wide range of length scales and occur when a layer of granular material becomes unstable. In the geophysical context rock-falls, landslides and snow slab avalanches may set up to 10 billion cubic metres of material in motion, whilst in industrial flows in silos, hoppers, rotating drums or on slag heaps the volume of material is of the order of several cubic centimetres to several hundreds of cubic metres. Despite the enormous difference in length scales the dominant physical mechanisms that drive the flow are similar. 

A granular bore

 I am interested in developing and extending mathematical models that describe the complete avalanche motion from initiation, on a steep slope, to run-out on a shallow slope. Many interesting features can be observed, such as the formation of shock waves (above).  The avalanche enters from the top-right at high speed and is rapidly brought to rest by a wall that is out of shot at the bottom-left side, a shock wave forms and propagates upslope at almost constant speed. As the material crosses the shock the avalanche thickness increases by a factor of twelve.  An animated version can be seen by clicking on one of the following links  (RealPlayer)   (Mpeg)  or  (Windows Media Player).



Gray, J.M.N.T. & Hutter, K. (1998). Physik granularer Lawinen. Physikalische Blatter 54(1), 37-43. 

Gray, J.M.N.T., Wieland, M. & Hutter K. (1999). Free surface flow of cohesionless granular avalanches over complex basal topography. Proc. Roy. Soc. 445 , 1841-1874.  

Wieland, M., Gray, J.M.N.T. & Hutter K. (1999). Channelised free surface flow of cohesionless granular avalanches in a chute with shallow lateral curvature. J. Fluid. Mech. 392 , 73-100. (pdf)  

Gray J.M.N.T., Tai Y.-C. & S. Noelle (2003) Shock waves, dead-zones and particle-free regions in rapid granular free surface flows. J. Fluid Mech. 491, 161-181. (pdf)


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Page last modified: December 22, 2000