8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Tue 611:23-14:00P9.17Effects of a nonuniform density profile upon the velocityflow and the viscosity of a shear thinning colloidaldispersionThomas Farage 1 and Joseph Brader 11 University of Fribourg, Département de Physique, Chemin du Musée 3 1700, Fribourg,SwitzerlandWithin the framework of the Mode Coupling Theory (MCT) for hard sphere Brownian particleswe investigate how an imposed nonuniform density profile affects both the velocity profiles (shearbanding) and local/bulk viscosity of a dispersion under shear. Our studies employ the schematicF ˙γ 12 mode-coupling theory [1, 2] (with the memory function of Brader et al. [3]) as a toy model tonumerically explore the consequences of a spatially varying volume fraction upon the rheologicalresponse. Our work is motivated by the very recent results of Fall et al. [4] and Besseling et al. [5]which have identified shear induced particle migration as an important mechanism underlying theflow of dense dispersions.[1] M. Fuchs, M. E. Cates, Physical Review Letters, 89, 248304 (2002).[2] M. Fuchs, M. E. Cates, Faraday Disc. 123, 267 (2003).[3] J. M. Brader, T. Voigtmann, M. Fuchs, R. G. Larson and M. E. Cates, PNAS, 106, 36, 15186(2009).[4] A. Fall, A. Lemaître, F. Bertrand, D. Bonn and G. Ovarlez, Physical Review Letters, 105,268303 (2010).[5] R. Besseling, L. Isa, P. Ballesta, G. Petekidis, M. E. Cates, and W. C. K. Poon, PhysicalReview Letters, 105, 268301 (2010).17