Shear-induced migration and orientation of rigid fibers in an oscillatory pipe flow

Advances in the Rheological Characterization of Slurries of Elongated Particles

“…For example, Mondy et al (1994) measured the spatial distribution of ellipsoids of aspect ratios A = 2 to 18.4 within a wide-gap Couette flow and found results similar to that for spheres. More recent measurements (Strednak et al, 2018) indicate that fibers migrate within tube flow, away from the walls and toward the center as expected from observations of spheres. However, significant migration occurs at much smaller volume fractions in suspensions of fibers as compared to spheres.…”

“…14 shows the position dependent concentration at steady-state for two different aspect ratios for suspensions at ϕ = 0.03, whereas Snook et al (2016) observed no particle migration for suspensions of spheres at ϕ < 0.1. Generally, Strednak et al (2018) found that the extent of migration for the rigid fibers was similar at the same value of nL 2 d = 4Aϕ/π, regardless of the aspect ratio.…”

“…Finally, there is a lack of detailed numerical and experimental work describing the microstructure at concentrations beyond the dilute limit and up to the jamming transition. The dependence of bulk rheological measurements on the changes in the microstructure of slurries of elongated particles in flow have been discussed (Franceschini et al, 2011;Snook et al, 2012;Tapia et al, 2017;Strednak et al, 2018). The changes in the microstructure are irreversible in concentrated suspensions which contradict the reversible nature of the Stokes equations, which govern their hydrodynamics.…”

“…Hence the normal stress differences originate with the particles, which must be present at a sufficiently high concentration for the normal stresses to be measurable. Non-zero normal stress differences can cause a number of effects, including shear-induced migration of particles within non-linear flows (Nott and Brady, 1994;Nott et al, 2011;Snook et al, 2016;Strednak et al, 2018).…”

Chemo-Physico-Mechanical Behavior of Class G Oil Well Cement Pastes

“…Previous work have shown that for pressure-driven and wall-driven flows of neutrally buoyant rod suspensions, the particles tend to migrate toward regions of low shear rate, see e.g. Mondy et al [268] and Strednak et al [269]. Although the PVA fibers considered in this study are lighter than the suspending cement paste, the same mechanisms can cause fiber concentration variations both within the measurement gap of the viscometer, and across the crosssection of a pipe or an annulus during and after placement of cement slurry.…”