The
strange case of shear-thinning in non-Brownian suspensions
Marco Ellero,
BCAM
– Basque Center for Applied Mathematics, Bilbao,
Spain
Abstract
Shear thinning is generally reported in Brownian suspensions where it is understood to arise from a decrease in the relative contribution of entropic forces. However it has also been often reported in experiments with non-colloidal systems and nominally-Newtonian matrices at high volume fractions. In spite of the generality of the observations, its origin is still a matter of debate and the behavior is difficult to reproduce in numerical simulations where shear thickening is typically observed instead.
Several explanations have been proposed in recent years ranging from hidden non-Newtonian effects in the small interparticle gaps [1,2], excluded volume effects [3] and variable friction coefficients [4,5]. Another possibility that has emerged recently is related to slip occurring in the interparticle gaps at the liquid-solid interface [6,7,8]. In this talk I will review some of these issues and recent theories developed in this context.
[1] "Shear thinning of noncolloidal suspensions", A Vázquez-Quesada, RI Tanner, M Ellero, Physical Review Letters 117 (10), 108001 (2016).
[2] "Investigating the causes of shear-thinning in non-colloidal suspensions: Experiments and simulations" A Vázquez-Quesada, A Mahmud, S Dai, M Ellero, RI Tanner, Journal of Non-Newtonian Fluid Mechanics 248, 1-7 (2017)
[3] "Shear thinning in non-Brownian suspensions " G. Chatte, J. Comtet, A. Nigues, L. Bocquet, A. Siria, G. Ducouret, F. Lequeux, N. Lenoir, G. Ovarlez, and A. Colin, Soft Matter 14, 879 (2018).
[4] "Shear thinning in non-Brownian suspensions explained by variable friction between particles", Lobry, L. and Gallier, S and Peters F J. Fluid Mech. 860:682–710 (2019)
[5] "A bootstrap mechanism for non-colloidal suspension viscosity", Roger I. Tanner, Christopher Ness, Arif Mahmud, Shaocong Dai & Jiyoung Moon Rheologica Acta volume 57, 635–643 (2018)
[6] "Slip on a particle surface as the possible origin of shear thinning in non-Brownian suspensions" M. Kroupa, M. Soos, and J. Kosek, Phys. Chem. Chem. Phys. 19, 5979 (2017).
[7] "Apparent slip mechanism between two spheres based on solvent rheology: Theory and implication for the shear thinning of non-Brownian suspensions" A Vázquez-Quesada, P Español, M Ellero, Physical Review Fluids 3 (12), 123302 (2018).
[8] "Numerical investigation of the rheological behavior of a dense particle suspension in a biviscous matrix using a lubrication dynamics method", S.S.P. Kumar, A.Vázquez-Quesad, M.Ellero, Journal of Non-Newtonian Fluid Mechanics, 281, 104312 (2020).
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