Shear-driven flow of athermal, frictionless, spherocylinder suspensions in two dimensions: Spatial structure and correlations

Abstract

We use numerical simulations to study the flow of athermal, frictionless, soft-core two dimensional spherocylinders driven by a uniform steady-state simple shear applied at a fixed volume and a fixed finite strain rateγ. Energy dissipation is via a viscous drag with respect to a uniformly sheared host fluid, giving a simple model for flow in a non-Brownian suspension with Newtonian rheology. We study the resulting spatial structure of the sheared system, and compute correlation functions of the velocity, the particle density, the nematic order parameter, and the particle angular velocity. Correlations of density, nematic order, and angular velocity are shown to be short ranged both below and above jamming. We compare a system of size-bidisperse particles with a system of sizemonodisperse particles, and argue how differences in spatial order as the packing increases leads to differences in the global nematic order parameter. We consider the effect of shearing on initially well ordered configurations, and show that in many cases the shearing acts to destroy the order, leading to the same steady-state ensemble as found when starting from random initial configurations. arXiv:2002.02348v2 [cond-mat.soft]

Shear-driven flow of athermal, frictionless, spherocylinder suspensions in two dimensions: Particle rotations and orientational ordering

“…The sharp drop in the magnitude S 2 to small values, as the system relaxes back to steady-state, demonstrates that the relaxation takes place through the incoherent rotation of individual particles, not a coherent rotation of many particles that would preserve the magnitude of the ordering. We will confirm the absence of long range coherence in particle orientations in a separate work [57] where we directly compute the spatial correlation function of S 2 and find it to be short ranged.…”

“…IV F, in which we modeled the system by an isolated particle being acted upon by an orientation dependent average elastic torque and random incoherent torque noise, indicates that correlations between particles are not important to describe the behavior of the system. We will give further evidence for this conclusion in a separate paper [57], where we directly compute the spatial correlation function for S 2 and show that is it short ranged. Several early works [9,10,13,18] considered the orientational ordering of particles in a shear flow by computing the probability density P(θ) for a given particle to be oriented at a particular angle θ i = θ.…”

Start-up shear of spherocylinder packings: effect of friction

“…Key finding was that frictional interaction forces supress alignment during shear. Similar systems have been studied in three [20,21] and two spatial dimensions [22][23][24]. Experimental work frequently considers the interplay of (frictional) contact and hydrodynamic forces in suspensions [25][26][27][28].…”