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SUMMARY:MechE Colloquium: Coupling rheology and segregation in granular fl
 ows
DTSTART:20210928T121500
DTEND:20210928T131500
DTSTAMP:20260406T020522Z
UID:e96fe1f171b3be6fec5985dcc5cf33ce7866ef09bc5b204843bc1c2f
CATEGORIES:Conferences - Seminars
DESCRIPTION:Prof. Nico Gray\, Department of Mathematics\, University of Ma
 nchester\, Invited Professor at the Environmental Hydraulics Laboratory (L
 HE) of the school of Architecture\, Civil and Environmental Engineering (E
 NAC)\nAbstract:\nDuring the last fifteen years there has been a paradigm s
 hift in the continuum modelling of granular materials\; most notably with 
 the development of rheological models\, such as the μ(I)-rheology (where 
 μ is the friction and I is the inertial number)\, but also with significa
 nt advances in theories for particle segregation. This paper details theor
 etical and numerical frameworks (based on OpenFOAM®) which unify these cu
 rrently disconnected endeavours. Coupling the segregation with the flow\, 
 and vice versa\, is not only vital for a complete theory of granular mater
 ials\, but is also beneficial for developing numerical methods to handle e
 volving free surfaces. This general approach is based on the partially reg
 ularized incompressible μ(I)-rheology\, which is coupled to the gravity-d
 riven segregation theory of Gray & Ancey (J. Fluid Mech.\, vol. 678\, 2011
 \, pp. 353–588).\nThese advection–diffusion–segregation equations de
 scribe the evolving concentrations of the constituents\, which then couple
  back to the variable viscosity in the incompressible Navier–Stokes equa
 tions. A novel feature of this approach is that any number of differently 
 sized phases may be included\, which may have disparate frictional propert
 ies. Further inclusion of an excess air phase\, which segregates away from
  the granular material\, then allows the complex evolution of the free sur
 face to be captured simultaneously. Three primary coupling mechanisms are 
 identified: (i) advection of the particle concentrations by the bulk veloc
 ity\, (ii) feedback of the particle-size and/or frictional properties on t
 he bulk flow field and (iii) influence of the shear rate\, pressure\, grav
 ity\, particle size and particle-size ratio on the locally evolving segreg
 ation and diffusion rates. The numerical method is extensively tested in o
 ne-way coupled computations\, before the fully coupled model is compared w
 ith the discrete element method simulations of Tripathi & Khakhar (Phys. F
 luids\, vol. 23\, 2011\, 113302) and used to compute the petal-like segreg
 ation pattern that spontaneously develops in a square rotating drum.\n\nLi
 nk to the paper: https://doi.org/10.1017/jfm.2020.973\nAnd movie: https://
 static.cambridge.org/content/id/urn:cambridge.org:id:article:S002211202000
 9738/resource/name/S0022112020009738sup006.mp4\n\nBio:\nNico Gray is a pro
 fessor of Applied Mathematics in the Department of Mathematics and the Man
 chester Centre for Nonlinear Dynamics at The University of Manchester. He 
 is an expert on granular flows and the particle segregation that takes pla
 ce within them. This has applications to a wide range of common industrial
  processes\, as well as to geophysical flows such as avalanches and debris
  flows. Nico holds a BSc in Mathematics from the University of  Mancheste
 r\, a PhD from the University of Cambridge and a Habilitation in Continuum
  Mechanics and Geophysical Mechanics from the Technical University of Darm
 stadt in Germany.
LOCATION:BM 5202 https://plan.epfl.ch/?room==BM%205202 https://epfl.zoom.u
 s/j/65093257313
STATUS:CONFIRMED
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