Effects of shear thinning on migration of neutrally buoyant particles in pressure driven flow of Newtonian and viscoelastic fluids

The pattern of cross stream migration of neutrally buoyant particles in a p ressure driven flow depends strongly on the properties of the suspending fl uid. These migration effects have been studied by direct numerical simulati on in planar flow. Shear thinning has a large effect when the inertia or el asticity is large, but only a small effect when they are small. At moderate Reynolds numbers, shear thinning causes particles to migrate away from the centerline, creating a particle-free zone in the core of the channel, whic h increases with the amount of shear thinning. In a viscoelastic fluid with shear thinning, particles migrate either toward the centerline or toward t he walls, creating an annular particle-free zone at intermediate radii. The simulations also give rise to precise determination of slip velocity distr ibutions in the various cases studied. (C)2000 Elsevier Science B.V. All ri ghts reserved.