Viscosity of particle laden films
1 Université Paris-Est, Laboratoire Navier (UMR CNRS 8205, École des Ponts ParisTech, IFSTTAR), 2, allée Kepler, 77420 Champs-Sur-Marne, France
2 Laboratoire Navier, Université Paris-Est, Laboratoire Navier (UMR CNRS 8205, École des Ponts ParisTech, IFSTTAR), 5 bd Descartes, 77 454 Champs-Sur-Marne, France
Published online: 30 June 2017
We perform retraction experiments on soap films where large particles bridge the two interfaces. Local velocities are measured by PIV during the unstationnary regime. The velocity variation in time and space can be described by a continuous fluid model from which effective viscosity (shear and dilatational) of particulate films is measured. The 2D effective viscosity of particulate films η2D increases with particle surface fraction ϕ: at low ϕ, it tends to the interfacial dilatational viscosity of the liquid/air interfaces and it diverges at the critical particle surface fraction ϕc ≃ 0.84. Experimental data agree with classical viscosity laws of hard spheres suspensions adapted to the 2D geometry, assuming viscous dissipation resulting from the squeeze of the liquid/air interfaces between the particles. Finally, we show that the observed viscous dissipation in particulate films has to be considered to describe the edge velocity during a retraction experiment at large particle coverage.
© The Authors, published by EDP Sciences, 2017
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