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SUMMARY:Modelling debris flow.
DTSTART:20230814T140000
DTEND:20230814T150000
DTSTAMP:20260407T014543Z
UID:6761f15385bc91ea89710ff66935e8c6a840505532c2dee15fc006e9
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Nico Gray\, Manchester University\, Invited Professeur a
 t LHE. Nico Gray is a Professor of Applied Mathematics in the Department o
 f Mathematics at the University of Manchester\, UK. He is an expert on gr
 anular flows and the particle segregation that takes place within them. Th
 is has applications to a wide range of industrial processes\, as well as t
 o geophysical flows such as snow avalanches and debris flows. Nico holds a
  BSc in Mathematics from the University of Manchester\, a PhD in Sea Ice D
 ynamics from the University of Cambridge and a Habilitation in Continuum M
 echanics and Geophysical Mechanics from the Technical University of Darmst
 adt in Germany. Prof. Gray is for one month at LHE for a visiting professo
 r stay.\nDebris flows are particle–fluid mixtures that pose a significan
 t hazard to many communities throughout the world. Bouldery debris flows a
 re often characterised by a deep dry granular flow front\, which is follow
 ed by a progressively thinner and increasingly watery tail. The formation 
 of highly destructive bouldery wave fronts is usually attributed to partic
 le-size segregation. However\, the moving-bed flume experiments of Davies 
 (N. Z. J. Hydrol.\, vol. 29\, 1990\, pp. 18–46) show that discrete surge
 s with dry fronts and watery tails also form in monodisperse particle–fl
 uid mixtures. These observations motivate the development of a new depth-a
 veraged mixture theory for debris flows\, which explicitly takes account o
 f the differing granular and phreatic surfaces\, velocity shear\, and rela
 tive motion between grains and fluid to explain these phenomena. The theor
 y consists of four coupled conservation laws that describe the spatial and
  temporal evolution of the grain and water thicknesses and depth-averaged 
 velocities. This system enables travelling wave solutions to be constructe
 d that consist of (i) a large amplitude dry flow front that smoothly trans
 itions to (ii) an undersaturated body\, (iii) an oversaturated region and 
 then (iv) a pure water tail. It is shown that these solutions are in good 
 quantitative agreement with Davies’ experiments at high bed speeds and s
 lope inclinations. At lower bed speeds and inclinations\, the theory produ
 ces travelling wave solutions that connect to a steady-uniform upstream fl
 ow\, and may or may not have a bulbous flow front\, consistent with Davies
 ’ observations.\n 
LOCATION:GC B1 10 https://plan.epfl.ch/?room==GC%20B1%2010
STATUS:CONFIRMED
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