Apparent slip mechanism between two spheres based on solvent rheology: Theory and implication for the shear thinning of non-Brownian suspensions
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Analytical results for the apparent slip between two spheres in a simple biviscous model of a shear thinning fluid are presented. Velocity profiles and apparent slip lengths along the surfaces are analyzed in order to characterize the physical mechanism. It is shown that in this non-Newtonian model, the effect of shear-thinning limited to high-shear rates in the interstitial regions between close spheres can be alternatively interpreted as the onset of an apparent shear-rate dependent slippage effect. The results of the theory compare well with experiments from the literature showing the presence of surface slip on a particle approaching a planar wall. In terms of implications on suspensions rheology, the present results bridge the ’hidden’ solvent shear-thinning theory [A. Va ́zquez-Quesada et al. , Phys. Rev. Lett., 117, 108001-5 (2016)] with slip-based models presented recently in [M. Kroupa et al., Phys. Chem. Chem. Phys. 19, 5979-5984 (2017)] as a possible explanation on the mechanism behind the shear-thinning in hard-sphere non-Brownian suspensions.