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SUMMARY:Coupling rheology and segregation in granular flows - Nico Gray\, 
 University of Manchester
DTSTART:20251113T113000Z
DTEND:20251113T123000Z
UID:TALK236677@talks.cam.ac.uk
CONTACT:Catherine Pearson
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 
 advances in theories for particle segregation. This paper details theoreti
 cal 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-rheology\, which is coupled to the gravity-driven segre
 gation theory of Gray & Ancey (J. Fluid Mech.\, vol. 678\, 2011\, pp. 353-
 588). These advection-diffusion-segregation equations describe the evolvin
 g concentrations of the constituents\, which then couple back to the varia
 ble viscosity in the incompressible Navier-Stokes equations. A novel featu
 re of this approach is that any number of differently sized phases may be 
 included\, which may have disparate frictional properties. Further inclusi
 on of an excess air phase\, which segregates away from the granular materi
 al\, then allows the complex evolution of the free surface to be captured 
 simultaneously. Three primary coupling mechanisms are identified: (i) adve
 ction of the particle concentrations by the bulk velocity\, (ii) feedback 
 of the particle-size and/or frictional properties on the bulk flow field a
 nd (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 compu
 tations\, before the fully coupled model is compared with the discrete ele
 ment method simulations of Tripathi & Khakhar (Phys. Fluids\, vol. 23\, 20
 11\, 113302) and used to compute the petal-like segregation pattern that s
 pontaneously develops in a square and triangular rotating drums.
LOCATION:Open Plan Area\, Institute for Energy and Environmental Flows\, M
 adingley Rise CB3 0EZ
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