Internal relaxation time in immersed particulate materials

Rognon, Pierre; Einav, Itai; Gay, Cyprien

doi:10.1103/physreve.81.061304

Cited by 18 publications

(18 citation statements)

References 52 publications

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“…We account for the deformability of the particles near the contact region by combining the above normal lubrication model with a linear elastic model via a Maxwell-type visco-elastic scheme ( [23], partly inspired by [26]) ( figure 4). The parameters are k n the contact stiffness and ν n (h) is the instantaneous viscosity of the interaction as defined in eq.…”

Section: Lubricationmentioning

confidence: 99%

Microscopic origins of shear stress in dense fluid–grain mixtures

2015

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A numerical model is used to simulate rheometer experiments at constant normal stress on dense suspensions of spheres. The complete model includes sphere-sphere contacts using a soft contact approach, short range hydrodynamic interactions defined by frame-invariant expressions of forces and torques in the lubrication approximation, and drag forces resulting from the poromechanical coupling computed with the DEM-PFV technique. Series of simulations in which some of the coupling terms are neglected highlight the role of the poromechanical coupling in the transient regimes. They also reveal that the shear component of the lubrication forces, though frequently neglected in the literature, has a dominant effect in the volume changes. On the other hand, the effects of lubrication torques are much less significant. The bulk shear stress is decomposed into contact stress and hydrodynamic stress terms whose dependency on a dimensionless shear rate-the so called viscous number I v -are examined. Both contributions are increasing functions of I v , contacts contribution dominates at low viscous number (I v < 0.15) whereas lubrication contributions are dominant for I v > 0.15, consistently with a phenomenological law infered by other authors. Statistics of microstructural variables highlight a complex interplay between solid contacts and hydrodynamic interac-B Bruno Chareyre tions. In contrast with a popular idea, the results suggest that lubrication may not necessarily reduce the contribution of contact forces to the bulk shear stress. The proposed model is general and applies directly to sheared immersed granular media in which pore pressure feedback plays a key role (triggering of avalanches, liquefaction).

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Section: Lubricationmentioning

confidence: 99%

Microscopic origins of shear stress in dense fluid–grain mixtures

2015

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“…In this section, we briefly present its main features, especially the modes of interaction accounted: grain elasticity, lubrication and surface repulsion. More details can be found in our previous works [17][18][19].…”

Section: Simulation Of a Model Dense Suspension With The Soft Dynmentioning

confidence: 99%

“…with p = 8 as discussed in [17]. More generally, torques or tangential forces between surfaces could be included, as well as complex features such as solid friction, adhesion and interfacial visco-elasticity, depending on the nature of the particles under consideration.…”

Section: Simulation Of a Model Dense Suspension With The Soft Dynmentioning

confidence: 99%

“…A cutoff value for the gap h is introduced as a way to avoid long range hydrodynamic interactions which are irrelevent to dense configurations: the particles interact only when h < 0.4d. Viscous and elastic torques are also included, as in [17].…”

Section: Simulation Of a Model Dense Suspension With The Soft Dynmentioning

confidence: 99%

“…This peculiar collective response can be understood from the microscopic relaxation time at the particle scale. As discussed in [17], each pair of particles behaves like a non-linear Maxwell analogue. The prescribed shear rate tends to separate their centers at a typical velocityγd.…”

Section: Collective Response To Shear: Importance Of Surface Repmentioning

confidence: 99%

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Flowing resistance and dilatancy of dense suspensions: lubrication and repulsion

2011

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8 pages - 5 figuresInternational audienceWe examine the flow properties of dense suspensions whose particles interact by viscous lubrication and surface repulsion. Using Soft Dynamics, we simulate its response to shear, prescribing the shear rate and the normal stress. We show that the behavior of steady flows can be described like that of dry grains, with a friction law and a dilatancy law. Their combination conveniently avoids the usual divergence of viscosity when approching the maximum packing fraction. However, the parameters of these laws depend in a non-trival way on the typical distance below which surfaces repel each other. The analysis of internal distribution of forces suggests a simple scenario underpining these complex dependencies. Pairs of particles appear to exchange a comparable lubrication force irrespective of their distance. This leads to a robust dynamic connected network controlling the collective resistance to flow

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Mobility in granular materials upon cyclic loading

Athani

Rognon

2018

Granular Matter

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Internal relaxation time in immersed particulate materials

Cited by 18 publications

References 52 publications

Microscopic origins of shear stress in dense fluid–grain mixtures

Microscopic origins of shear stress in dense fluid–grain mixtures

Flowing resistance and dilatancy of dense suspensions: lubrication and repulsion

Mobility in granular materials upon cyclic loading

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