Viscometric flow of dense granular materials under controlled pressure and shear stress

Abstract

Abstract

Interplay between hysteresis and nonlocality during onset and arrest of flow in granular materials

“…Although velocity-driven DEM simulations of plane shear flow are the norm 7 , such simulations miss important features of the flow-arrest transition 51 . To our knowledge, stress-driven plane shear simulations have only been implemented in very few studies either through a solid wall 52,53 , which corresponds to our setup, or through shearing of the periodic boundaries [54][55][56][57] . Finally, the pressure at the top wall is maintained close to a target value P w through a widely used feedback law 11 according to which the distance H between the walls evolves asḢ = (P w + σ zz (z = 0,t))L/g w , where the instantaneous normal stress σ zz exerted by the flowing grains is directly evaluated at the wall, and g w is a damping parameter that we take as g w = 100(mk n ) 1/2 .…”

Fluctuations and power-law scaling of dry, frictionless granular rheology near the hard-particle limit

“…Naturally, the goal is to develop a robust continuum description that can be used as a predictive tool for a wide variety of natural and technological processes, including scale-up. Further development of such continuum descriptions include wall effects [5], higher order rheological effects [6], fluctuations and non-local effects [7]. However, the reduction of the shear and strain rate tensors to µ and I, respectively, loses information that is important for distinguishing many rheological behaviors.…”

“…The lack of coaxiality between principal directions of stress and strain rate tensors in viscometric flows [10][11][12][13] contributes to those effects. Srivastava et al [6] developed a second-order rheological model that does not assume coaxiality of stress and strain rate tensors, which is important for capturing the role of inter-particle friction on granular rheology. Tensorial expressions of shear and strain rate are also important for describing the influence of loading geometries, as shown by Clemmer et al [14] in irrotational loading geometries of granular flows, where Drucker-Prager [15] type models can be insufficient.…”

“…Tensorial expressions of shear and strain rate are also important for describing the influence of loading geometries, as shown by Clemmer et al [14] in irrotational loading geometries of granular flows, where Drucker-Prager [15] type models can be insufficient. A goal of this paper is to understand the effect of pressure and system size N on the tensorial second-order rheological model [6], without the added contributions due to frictional contacts or suspensions.…”

“…Fitting such power laws require large amounts of robust data. In this paper, we examine frictionless granular flows for a large range of N , P and I, and study the effect of N and P on tensorial granular rheology [6] and its intrinsic fluctuations.…”