Coupling rheology and segregation in granular flows

Abstract

Abstract

An experimental scaling law for particle-size segregation in dense granular flows

“…Certainly, the theory has the right pressure dependence in the segregation and diffusion terms to capture the suppression of segregation in Golick & Daniels' (2009) annular shear-cell experiments, and Fry et al's (2019) DPM simulations, when a weight is added to the top plate. In addition, Barker et al (2021) have coupled the empirical segregation law (9.1) to the partially regularized μ(I)-rheology , and used it to compute the segregation in a square rotating drum. The results show that the empirical law can capture the qualitative development of the segregation patterns that form in the drum.…”

“…The fully coupled simulations of Barker et al (2021) make it clear that one of the key advantages of the oscillatory shear cell is that the bulk motion of the grains is prescribed rather than being free to evolve as part of the experiment. This eliminates many of the problems posed by sidewall friction (Jop et al 2005) as well as the more subtle feedback of the evolving particle-size distribution on the bulk flow field (see e.g.…”

“…In particular, the velocity profile u(z, t), shear ratė γ (z, t) and solids volume fraction Φ(z, t) are functions of space and time. In chute flows, Rognon et al (2007), Tripathi & Khakhar (2011 and Barker et al (2021) have shown that segregation-induced frictional feedbacks are responsible for marked deviations away from the classical monodisperse Bagnold velocity profile (Silbert et al 2001;GDR-MiDi 2004;Jop et al 2006). These feedbacks will in turn change the local shear rate and hence the time scale for particles to segregate and diffuse.…”

“…Complex interactions between the shear flow and an underlying static, or slowly moving region of grains, can lead to the development of amazing patterns in the deposit (e.g. Williams 1968;Gray & Hutter 1997;Baxter et al 1998;Hill et al 1999;Barker et al 2021). However, for a steady-state flow on a fixed base, an inversely graded particle-size distribution develops, with the large particles concentrated at the top of the flow and the finer grains concentrated near the base.…”

Drag, diffusion and segregation in inertial granular flows

“…2020; Barker et al. 2021). This is very close to the scaling that we predict due to the dependence of just the drag on pressure, suggesting again that the driving segregation force depends only very weakly on pressure () in these flows.…”