Simulations of flow induced ordering in viscoelastic fluids

In this thesis we report on simulations of colloidal ordering phenomena in shearthinning viscoelastic fluids under shear flow. Depending on the characteristics of the fluid, the colloids are observed to align in the direction of the flow. These string-like structures remain stable as long as the shear rate exceeds a critical value. This phenomenon has been subject of study for over 30 years, both theoretically and experimentally, because of to its importance in many technological processes, as for example in the food and cosmetics industry. Nevertheless, the mechanism driving the colloids to the aligned configuration has not yet been elucidated. The goal of this study is to simulate the alignment of colloids during shear flow in polymeric fluids with viscoelastic behavior. Besides that, colloid migration in confined systems was also investigated. A coarse-grained method based on Brownian dynamics was used, where every polymeric chain is modeled as a single particle. With these simulations we are able to obtain new insights and a better understanding for this ordering behavior.