SUMMARY

The characteristics of fibers suspensions depend on the properties of fibers, the suspending fluid, and fiber-fiber interactions. The thesis demonstrates the development and application of a novel coupled method (lattice Boltzmann and finite element methods) to investigate these relationships. It is hypothesized that particle aspect ratio and flexibility could significantly affect particle orientation and rheology of suspensions such as relative viscosity. Fibers are modeled as flexible rod particles which are obtained by finite element method. The fluid flow that causes the fibers to deform is calculated by lattice Boltzmann method. The method is extended from two dimensional case to three dimensional case. Results from simulation show the rigid fiber in simple shear flow produce a good agreement for orientation of a fiber relative to the theoretical study by Jeffery (1922). The flexible fiber exhibits an increase on the rotational period from the rigid fiber due to more deformation shape is revealed during rotation. The simulation technique demonstrates the ability to create fiber-fiber interactions to further study of relative viscosity of suspensions in shear flow. Simulation results show that fiber characteristics (fiber aspect ratio, fiber flexibility, and volume fractions) depend on the fiber orientation and the relative viscosities. The results are verified against known experimental measurement and theoretical results. The broad aim of this research is to better understand the behavior of fibers in fluid flow. It is hoped that future researchers may benefit from the new technique and algorithms developed here.