Couette flow of two-dimensional foams
Kamerlingh Onnes Laboratorium, Universiteit Leiden - P.O. Box 9504, 2300 RA Leiden, The Netherlands, EU
2 Instituut Lorentz, Universiteit Leiden - P.O. Box 9506, 2300 RA Leiden, The Netherlands, EU
Corresponding author: email@example.com
Accepted: 28 May 2010
We experimentally investigate flow of quasi–two-dimensional disordered foams in Couette geometries, both for foams squeezed below a top plate and for freely floating foams (bubble rafts). With the top plate, the flows are strongly localized and rate dependent. For the bubble rafts the flow profiles become essentially rate independent, the local and global rheology do not match, and in particular the foam flows in regions where the stress is below the global yield stress. We attribute this to nonlocal effects and show that the “fluidity” model recently introduced by Goyon et al. (Nature, 454 (2008) 84) captures the essential features of flow both with and without a top plate.
PACS: 47.57.Bc – Foams and emulsions / 83.60.Fg – Shear rate dependent viscosity / 83.10.Gr – Constitutive relations
© EPLA, 2010