Eur. Phys. J. E (2015) 38: 46
https://doi.org/10.1140/epje/i2015-15046-y

Regular Article

Apparent wall slip in non-Brownian hard-sphere suspensions

¹ Department of Applied Physics, School of Science, Aalto University, P.O. Box 11100, FI-00076, Aalto, Finland
² Department d’Estructura i Constituents de la Matèria. Facultat de Fìsica, Universitat de Barcelona, Martí i Franquès 1, E-08028, Barcelona, Spain

^* e-mail: mikael.mohtaschemi@aalto.fi

Received: 21 November 2014
Revised: 3 February 2015
Accepted: 31 March 2015
Published online: 25 May 2015

Abstract

We analyze apparent wall slip, the reduction of particle concentration near the wall, in hard-sphere suspensions at concentrations well below the jamming limit utilizing a continuum level diffusion model. The approach extends a constitutive equation proposed earlier with two additional potentials describing the effects of gravitation and wall-particle repulsion. We find that although both mechanisms are shear independent by nature, due to the shear-rate-dependent counter-balancing particle migration fluxes, the resulting net effect is non-linearly shear dependent, causing larger slip at small shear rates. In effect, this shows up in the classically measured flow curves as a mild shear thickening regime at the transition from small to intermediate shear rates.