Nonlinear-Flow-Induced Structure in Fiber Suspensions

Cornell University, Ithaca NY

Investigators

Abstract

Abstract CTS-9910908 D. L. Koch, Cornell University The rheological behavior of such complex fluids as fiber suspensions, crystal polymers, etc. are important in the paper, food, and pharmaceutical industries. Linear solutions exist for a number of these flows, but for many applications, nonlinear terms become important and must be included. It is proposed to study thee nonlinearities in the context of four situations highlighting viscoelasticity, fluid inertia, electrical double layer interactions, and fiber-fiber adhesion: i) Oscillatory linear flows do not show any change of orientation from one cycle to the next: there is, however, a cumulative drift of orientation when non-linear terms appear. Three such cases will be studied for a wide range of amplitude and frequency. ii) The case of fibers suspended in fluids emphasizes the inertia forces when considering their length (high Reynolds numbers), but viscous effects may dominate when the fiber diameter is the relevant dimension (Reynolds numbers near unity). A slender body theory will be developed and applied to the case of a single rotating fiber in a Couette flow. iii) Electrically charged rods are expected to interact with ions of opposite charge, with their resulting effect on the rod orientation. Experiments are planned to test the PI's earlier theoretical work on electoviscous effects. iv) Dense suspensions bring together viscous effects (fluid-body surface interaction) and Columbic friction laws (body-body contact). Such interactions will be studied with special attention to adhesive fiber-fiber contact.