Viscoelasticity-Induced Onset of Slip at the Wall for Polymer Fluids

Abstract

The progressive onset of slip at the wall, which corresponds to a slip length increasing with the solicitation time before reaching a plateau, has been investigated for model viscoelastic polymer solutions, allowing one to vary the longest relaxation time while keeping constant solid–fluid interactions. A hydrodynamic model based on a Maxwell fluid and the classical Navier’s hypothesis of a linear response for the friction stress at the interface fully accounts for the data. In the limit of the linear viscoelasticity of the fluid, we could postulate a Newtonian response for the interfacial friction coefficient, reflecting the local character of solid–liquid friction mechanisms. Deviations between the experiments and our model are observed when the fluid is far from its linear viscoelastic behavior.

Slip and Friction Mechanisms at Polymer Semi-Dilute Solutions/Solid Interfaces

“…As recently reported [31], a transient onset of slip at small shear times was observed for all investigated solutions. This transient onset of slip has been shown to result from the initial viscoelastic response of the solutions to the sudden onset of the shear, and to last for 5τ rep [31]. In the present paper, we focus on the steady state regime of slippage, corresponding to shear times larger than 5τ rep .…”

“…Series of semi-dilute solutions of a high molar mass polystyrene (PS) with chosen polymer volume fraction φ in diethyl phthalate (DEP), a non-volatile solvent, have been used, so that the polymer volume fraction could be kept constant during the duration of the flow characterization experiments. The protocol used to prepare the solutions is detailed in [31]. We briefly recall here its main steps.…”

“…Despite its strong interest in many situations such as enhanced oil recovery, cosmetics, and the food industry, the case of semi-dilute polymer solutions still remains poorly understood. Only few experimental data are available, ,,,− and they lead to contradictory conclusions.…”

Fast increase of nanofluidic slip in supercooled water: the key role of dynamics

“…[26][27][28][29][30][31][32][33] Further work has been performed to study the impact on friction of different wall features such as wettability, 34,35 roughness, 36 crystallographic orientation, 37 electronic structure, [38][39][40] or electrostatic interactions. 41 Yet a large number of questions with regard to the interface properties, such as its viscoelastic or purely viscous nature [42][43][44] or the possible link with its interfacial thermal transport equivalents via wall's wetting properties, [45][46][47] remain open nowadays, limiting the perspectives for a rational search of optimal interfaces.…”

Near-surface rheology and hydrodynamic boundary condition of semi-dilute polymer solutions

“…28 Relatively few studies have been performed on semi-dilute, unentangled polymer solutions where the slip lengths may be smaller. Indeed, some of the most recent velocimetry techniques for the investigation of near-wall polymer dynamics 29,30 are limited to micron-scale slip lengths. As will be shown below, however, there is a rich phenomenology below micrometric scales.…”