scholarly journals Segregation of large particles in dense granular flows suggests a granular Saffman effect

2018 ◽  
Vol 3 (7) ◽  
Author(s):  
K. van der Vaart ◽  
M. P. van Schrojenstein Lantman ◽  
T. Weinhart ◽  
S. Luding ◽  
C. Ancey ◽  
...  
Keyword(s):  
Granular Flows ◽  
Large Particles ◽  
Dense Granular Flows

scholarly journals Segregation-induced finger formation in granular free-surface flows

2016 ◽  
Vol 809 ◽  
pp. 168-212 ◽  
Author(s):  
J. L. Baker ◽  
C. G. Johnson ◽  
J. M. N. T. Gray
Keyword(s):  
Granular Flows ◽  
Free Surface Flows ◽  
Pyroclastic Flows ◽  
Coarse Grained ◽  
Momentum Balance ◽  
Large Particles ◽  
Averaged Model ◽  
Well Posed ◽  
Dense Granular Flows ◽  
New System

Geophysical granular flows, such as landslides, pyroclastic flows and snow avalanches, consist of particles with varying surface roughnesses or shapes that have a tendency to segregate during flow due to size differences. Such segregation leads to the formation of regions with different frictional properties, which in turn can feed back on the bulk flow. This paper introduces a well-posed depth-averaged model for these segregation-mobility feedback effects. The full segregation equation for dense granular flows is integrated through the avalanche thickness by assuming inversely graded layers with large particles above fines, and a Bagnold shear profile. The resulting large particle transport equation is then coupled to depth-averaged equations for conservation of mass and momentum, with the feedback arising through a basal friction law that is composition dependent, implying greater friction where there are more large particles. The new system of equations includes viscous terms in the momentum balance, which are derived from the $\unicode[STIX]{x1D707}(I)$-rheology for dense granular flows and represent a singular perturbation to previous models. Linear stability calculations of the steady uniform base state demonstrate the significance of these higher-order terms, which ensure that, unlike the inviscid equations, the growth rates remain bounded everywhere. The new system is therefore mathematically well posed. Two-dimensional simulations of bidisperse material propagating down an inclined plane show the development of an unstable large-rich flow front, which subsequently breaks into a series of finger-like structures, each bounded by coarse-grained lateral levees. The key properties of the fingers are independent of the grid resolution and are controlled by the physical viscosity. This process of segregation-induced finger formation is observed in laboratory experiments, and numerical computations are in qualitative agreement.

scholarly journals Self-diffusion scalings in dense granular flows

Soft Matter ◽  
2021 ◽  
Author(s):  
Riccardo Artoni ◽  
Michele Larcher ◽  
James T. Jenkins ◽  
Patrick Richard
Keyword(s):  
Shear Rate ◽  
Solid Fraction ◽  
Granular Flows ◽  
The Self ◽  
Granular Temperature ◽  
Restitution Coefficient ◽  
Self Diffusion ◽  
Diffusivity Tensor ◽  
Dense Granular Flows

The self-diffusivity tensor in homogeneously sheared dense granular flows is anisotropic. We show how its components depend on solid fraction, restitution coefficient, shear rate, and granular temperature.

Shock waves in dense granular flows down a chute

Shock Waves ◽  
2007 ◽  
Vol 17 (5) ◽  
pp. 337-349 ◽  
Author(s):  
Piroz Zamankhan
Keyword(s):  
Shock Waves ◽  
Granular Flows ◽  
Dense Granular Flows

Shear induced diffusion in dense granular flows

2010 ◽  
Author(s):  
Ashish V. Orpe ◽  
Chris H. Rycroft ◽  
Arshad A. Kudrolli ◽  
Joe Goddard ◽  
Pasquale Giovine ◽  
...  
Keyword(s):  
Granular Flows ◽  
Dense Granular Flows

scholarly journals Numerical tests of constitutive laws for dense granular flows

2005 ◽  
Vol 72 (5) ◽  
Author(s):  
Gregg Lois ◽  
Anaël Lemaître ◽  
Jean M. Carlson
Keyword(s):  
Granular Flows ◽  
Constitutive Laws ◽  
Numerical Tests ◽  
Dense Granular Flows
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