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CATEGORIES:Fluid Mechanics (DAMTP)
SUMMARY:Particle size segregation and spontaneous levee fo
 rmation in geophysical mass flows - Nico Gray (Man
 chester)
DTSTART;TZID=Europe/London:20111104T160000
DTEND;TZID=Europe/London:20111104T170000
UID:TALK33044AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/33044
DESCRIPTION:Hazardous geophysical mass flows\, such as snow av
 alanches\, debris-flows and pyroclastic flows\, of
 ten spontaneously develop large particle rich leve
 es that channelize the flow and enhance their run-
 out. Measurements of the surface velocity near an 
 advancing flow front have been made at the United 
 States Geological Survey (USGS) debris-flow flume\
 , where 10m$^3$ of water saturated sand and gravel
  are allowed to flow down an 80m chute onto a run-
 out pad. In the run-out phase the flow front is ap
 proximately invariant in shape and advances at alm
 ost constant speed. By tracking the motion of surf
 ace tracers and using a simple kinematic model\, i
 t was possible to infer bulk motion as incoming ma
 terial is sheared towards the front\, over-run and
  shouldered to the side. At the heart of the levee
  formation process is a subtle segregation-mobilit
 y feedback effect. Simple models for particle segr
 egation and the depth-averaged motion of granular 
 avalanches are described and one of the first atte
 mpts is made to couple these two types of models t
 ogether. This process proves to be non-trivial\, y
 ielding considerable complexity as well as patholo
 gies that require additional physics to be include
 d.\n
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberfor
 ce Road\, Cambridge
CONTACT:Dr Ed Brambley
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