Numerical Simulation of Flow Kinematics for Suspensions Containing Continuously-Dispersed Aspect-Ratio Fibers

International audienceFiber suspension flow and fiber orientation through a parallel- plate channel were numerically simulated for fiber suspensions including continuously dispersed aspect ratios from 10 to 50. In the simulations, both the fiber–fiber and fiber–wall interactions were not taken into account. A statistical scheme that proceeds by evaluating the orientation evolution of a large number of fibers from the solution of the Jeffery equation along the streamlines was confirmed to be a very useful and feasible method to accurately analyze the orientation distribution of fibers with continuously dispersed aspect ratios. For monodisperse suspensions with small-aspect-ratio fibers, flip-over or oscillation phenomenon of the orientation ellipsoid caused the wavy patterns of the velocity profile and the streamlines as well as the abrupt and complex variation of the shear stress and the normal stress difference near the channel wall as proven in one of our former works. On the other hand, continuous dispersions containing from small- to large-aspect-ratio fibers were able to induce smoother evolutions of the fiber orientation and the flow kinematics. In the processing of fiber composites, the length of suspended fibers is always continuously distributed because of fiber breakage during processing; thus, the smooth evolutions of the flow kinematics and the stress distribution can be attained