Structure formation of non-colloidal particles in viscoelastic fluids subjected to simple shear flow

The alignment and the aggregation of particles in a viscoelastic fluid in simple shear flow are qualitatively analyzed, using a two-dimensional direct numerical simulation. Depending on shear-thinning, solvent viscosity and Weissenburg number, a typical sequence in structural transitions from random particle configuration to string formation is found with clustering and clustered string formation in between. The solvent viscosity and the Weissenburg number, thereby the ratio of normal stress to shear stress, are found the most influential parameters forthe onset of string formation. The influence of shear-thinning is less clear. More shear-thinning seems to promote string formation if the stress ratio is kept constant. The angular velocity of particles is reduced by approximately 60%, when particles form a string, independently of the parameters used.