Fluidisation and plastic activity in a model soft-glassy material flowing in micro-channels with rough walls

¹ Forschungszentrum Jülich GmbH, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11) - Fürther Straße 248, 90429 Nürnberg, Germany
² Department of Physics and INFN, University of Tor Vergata - Via della Ricerca Scientifica 1, 00133 Rome, Italy
³ Istituto per le Applicazioni del Calcolo CNR - Via dei Taurini 9, 00185 Roma, Italy

Received: 4 April 2016
Accepted: 5 July 2016

Abstract

By means of mesoscopic numerical simulations of a model soft-glassy material, we investigate the role of boundary roughness on the flow behaviour of the material, probing the bulk/wall and global/local rheologies. We show that the roughness reduces the wall slip induced by wettability properties and acts as a source of fluidisation for the material. A direct inspection of the plastic events suggests that their rate of occurrence grows with the fluidity field, reconciling our simulations with kinetic elasto-plastic descriptions of jammed materials. Notwithstanding, we observe qualitative and quantitative differences in the scaling, depending on the distance from the rough wall and on the imposed shear. The impact of roughness on the orientational statistics is also studied.