Investigation of shear banding in three-dimensional foams

Abstract

We study the steady flow properties of different three-dimensional aqueous foams in a wide-gap Couette geometry. From local velocity measurements through Magnetic Resonance Imaging (MRI) techniques and from viscosity bifurcation experiments, we find that these foams do not exhibit any observable signature of shear banding. This contrasts with two previous results (Rodts S. et al., Europhys. Lett., 69 (2005) 636 and Da Cruz F. et al., Phys. Rev. E, 66 (2002) 051305); we discuss possible reasons for this discrepancy. Moreover, the foams we studied undergo steady flow for shear rates well below the critical shear rate recently predicted (Denkov D. et al., Phys. Rev. Lett., 103 (2009) 118302). Local measurements of the constitutive law finally show that these foams behave as simple Herschel-Bulkley yield stress fluids.