Abstract
Particle segregation in geophysical and industrial granular flows is typically driven by gravity and shear. While gravity-induced segregation is relatively well understood, shear-induced segregation is not. In particular, what controls segregation in the absence of gravity and the interplay between shearand gravity-driven segregation remain unclear. Here, we explore the shear-induced segregation force on an intruder particle in controlled-velocity granular flows where the shear profile is systematically varied. The shear-induced segregation force is found to be proportional to the shear rate gradient, which effectively pushes the large intruder from lower to higher shear rate regions. A scaling law is developed for the segregation force that is accurate over a wide range of overburden pressures and shear rates, and hence inertial numbers.
Highlights
2 MethodsGranular materials consisting of different particle species 2.1 Velocity-controlled flow tend to segregate by species size, density, and other properties, which is of great importance in many geophysical and industrial problems [1, 2]
We study shear-induced segregation by determining the net segregation force Fseg acting on an intruder particle for various shear rate profiles
Intruder displacement is driven by the net segregation force Fseg, which depends on the shear rate gradient ∂γ /∂z
Summary
Granular materials consisting of different particle species 2.1 Velocity-controlled flow tend to segregate by species size, density, and other properties, which is of great importance in many geophysical and industrial problems [1, 2]. We computationally explore shear-induced segregation using controlled-velocity flows, where a desired velocity profile is imposed via a stabilizing force algorithm [12]. We measure the net segregation force on an intruder particle in various flows with systematically varied shear rate gradients, in the absence of gravity, and therefrom develop a scaling law for shear-induced segregation forces in terms of the shear rate gradient and other flow conditions. Controlled-velocity flow has been previously applied to study granular rheology [14,15,16] and segregation induced by gravity [12, 17, 18], but it has not been used to explore segregation induced purely by shear.
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