Analysis of rheological properties of fiber suspensions in a Newtonian fluid by direct fiber simulation. Part 3: Behavior in uniaxial extensional flows

The present work presents a predictive direct fiber simulation of fiber suspensions under uniaxial extensional flows by Stokesian dynamics, considering both near- and farfield hydrodynamic intrafiber interactions and lubrication approximation for interfibers. Initially, code validation is performed and simulation predictions compared with experimental data. Afterwards, the orientation tensor under flow is discussed as a function of volume fraction, aspect ratio and flexibility. Based on the results, a general constitutive equation with a proposed parameter is proposed and verified by comparing experimental data of high volume fraction and high aspect ratio systems.