title: Wall slip across the jamming transition of soft thermoresponsive particles.
abstract: Flows of suspensions are often affected by wall slip, that is, the fluid velocity v(f) in the vicinity of a boundary differs from the wall velocity v(w) due to the presence of a lubrication layer. While the slip velocity v(s)=|v(f)-v(w)| robustly scales linearly with the stress σ at the wall in dilute suspensions, there is no consensus regarding denser suspensions that are sheared in the bulk, for which slip velocities have been reported to scale as a v(s)∝σ(p) with exponents p inconsistently ranging between 0 and 2. Here we focus on a suspension of soft thermoresponsive particles and show that v(s)) actually scales as a power law of the viscous stress σ-σ(c), where σ(c) denotes the yield stress of the bulk material. By tuning the temperature across the jamming transition, we further demonstrate that this scaling holds true over a large range of packing fractions ϕ on both sides of the jamming point and that the exponent p increases continuously with ϕ, from p=1 in the case of dilute suspensions to p=2 for jammed assemblies. These results allow us to successfully revisit inconsistent data from the literature and pave the way for a continuous description of wall slip above and below jamming.
authors.affiliation: Centre de Recherche Paul Pascal, CNRS UPR 8641-115 avenue Dr. Schweitzer, 33600 Pessac, France.
authors.forename: Thibaut
authors.initials: T
authors.lastname: Divoux
authors.affiliation: Université de Bordeaux, ISM, IPB, 33607 Pessac Cedex, France.
authors.forename: Véronique
authors.initials: V
authors.lastname: Lapeyre
authors.affiliation: Université de Bordeaux, ISM, IPB, 33607 Pessac Cedex, France.
authors.forename: Valérie
authors.initials: V
authors.lastname: Ravaine
authors.affiliation: Université de Lyon, Laboratoire de Physique, École Normale Supérieure de Lyon, CNRS UMR 5672, 46 Allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Manneville