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SUMMARY:Multiscale Modelling of Granular Flows - Krishna Kumar
DTSTART:20131121T160000Z
DTEND:20131121T170000Z
UID:TALK47405@talks.cam.ac.uk
CONTACT:Jen Fusiello
DESCRIPTION:Geophysical hazards\, such as avalanches\, debris flows and su
 bmarine landslides\, involve rapid mass movement of granular solids\, wate
 r and air as a single-phase system. The momentum transfer between the disc
 rete and continuous phases significantly affects the dynamics of the flow.
  The dynamics of a granular flow involve at least three distinct scales:th
 e microscopic scale\, which is characterised by contact between particles\
 , the meso-scale\, which represents micro-structural effects such as parti
 cle rearrangement\, and the macroscopic scale. This study aims to understa
 nd the ability of continuum models in capturing the micro-mechanism of gra
 nular flow dynamics. The initiation and propagation of granular flows depe
 nd mainly on the slope\, density\, and quantity of the material destabilis
 ed. Material Point Method (MPM)\, a hybrid Lagrangian and Eulerian approac
 h is used to describe the continuum behaviour of granular flow dynamics\, 
 while the micro-mechanics is captured using Discrete Element Method (DEM) 
 with tangential contact force model.\n\nMost macroscopic models are able t
 o capture simple mechanical behaviours\, however the complex physical mech
 anisms that occur at the grain scale\, such as hydrodynamic instabilities\
 , the formation of clusters\, collapse\, and transport\, have largely been
  ignored. In order to describe the mechanism of saturated and/or immersed 
 granular flows\, it is important to consider both the dynamics of the soli
 d phase and the role of the ambient fluid. Two-dimensional sub-grain scale
  numerical simulations are performed to understand the local rheology of a
  dense granular flows in fluid. Discrete Element Method is coupled with th
 e Lattice Boltzmann Method (LBM) for fluid-grain interactions\, to underst
 and the evolution of immersed granular flows. A parametric analysis is per
 formed to assess the influence of the grain sample characteristics (initia
 l configuration\, permeability\, slope of inclined plane) on the evolution
  of flow and run-out distances. The effect of hydrodynamic forces and hydr
 oplaning on the run-out evolution is analysed by comparing the mechanism o
 f energy dissipation and flow evolution in dry and immersed granular flows
 \n
LOCATION: Cambridge University Engineering Department\, Lecture Room 5
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