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SUMMARY:Coupling rheology and segregation in granular flows - Nico Gray\, 
 University of Manchester
DTSTART:20220429T150000Z
DTEND:20220429T160000Z
UID:TALK173459@talks.cam.ac.uk
CONTACT:Prof. Jerome Neufeld
DESCRIPTION:During the last fifteen years there has been a paradigm shift 
 in the continuum modelling of granular materials\; most notably with the d
 evelopment of rheological models\, such as the μ(I)-rheology (where μ is
  the friction and I is the inertial number)\, but also with significant ad
 vances in theories for particle segregation. This paper details theoretica
 l and numerical frameworks (based on OpenFOAM®) which unify these current
 ly disconnected endeavours. Coupling the segregation with the flow\, and v
 ice versa\, is not only vital for a complete theory of granular materials\
 , but is also beneficial for developing numerical methods to handle evolvi
 ng free surfaces. This general approach is based on the partially regulari
 zed incompressible μ(I)-rheology\, which is coupled to the gravity-driven
  segregation theory of Gray & Ancey (J. Fluid Mech.\, vol. 678\, 2011\, pp
 . 535–588). These advection–diffusion–segregation equations describe
  the evolving concentrations of the constituents\, which then couple back 
 to the variable viscosity in the incompressible Navier–Stokes equations.
  A novel feature of this approach is that any number of differently sized 
 phases may be included\, which may have disparate frictional properties. F
 urther inclusion of an excess air phase\, which segregates away from the g
 ranular material\, then allows the complex evolution of the free surface t
 o be captured simultaneously. Three primary coupling mechanisms are identi
 fied: (i) advection of the particle concentrations by the bulk velocity\, 
 (ii) feedback of the particle-size and/or frictional properties on the bul
 k flow field and (iii) influence of the shear rate\, pressure\, gravity\, 
 particle size and particle-size ratio on the locally evolving segregation 
 and diffusion rates. The numerical method is extensively tested in one-way
  coupled computations\, before the fully coupled model is compared with th
 e discrete element method simulations of Tripathi & Khakhar (Phys. Fluids\
 , vol. 23\, 2011\, 113302) and used to compute the petal-like segregation 
 pattern that spontaneously develops in a square rotating drum.\n\nT. Barke
 r\, M. Rauter\, E. S. F. Maguire\, C. G. Johnson & J. M. N. T. Gray (2021)
  Coupling rheology and segregation in granular flows. J. Fluid Mech. 909\,
  A22. https://doi.org/10.1017/jfm.2020.973\n\nT. Trewhela\, C. Ancey & J. 
 M. N. T. Gray (2021) An experimental scaling law for particle-size segrega
 tion in dense granular flows. J. Fluid Mech. 916\, A55. https://doi.org/10
 .1017/jfm.2021.227\n\nSupplementary movie:\n\nhttps://static.cambridge.org
 /content/id/urn:cambridge.org:id:article:S0022112020009738/resource/name/S
 0022112020009738sup006.mp4
LOCATION:MR2\, Centre for Mathematical Sciences\, Wilberforce Road\, Cambr
 idge
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