Numerical Simulation Of Fiber Suspensions Through A Slit Channel Containing A Cylinder

Fiber suspensions occur in natural phenomena and industrial process variously. The investigation of fiber suspensions has received much attention because it's useful in production of composite materials, environmental engineering, chemical engineering, paper making, textile engineering and so on. Meanwhile, the mechanical, thermal and electrical properties of the corresponding fiber composite are highly sensitive to the orientation distribution. It is significant to understand the fiber orientation distribution in the flow.The motion of fiber in the channel with squeeze-expansion flow, such as the flow through a slit channel containing a cylinder, is one representative kind of complex suspension flow. In this paper, the finite difference method is used to calculate the flow velocity. Based on the slender-body theory, LAGERAGIAN model is employed to predict the fiber orientation distribution. The fiber orientation distributions in a suspension flow through a slit channel containing a cylinder were predicted. The effects of different Reynolds number, obstacle, initial fiber orientation, stokes numbers and the fiber aspect-ratio were studied. Some computational results are compared with the experimental data, and the good agreement is achieved. The results show that the fibers are perfectly aligned along the flow direction due to the elongational flow near the centerline downstream of the cylinder. Special emphasis is put on the function of Reynolds number on the fiber orientation distribution. It is found that Reynolds number has significant effect on the fiber orientation distribution only in the wake region behind the cylinder. The orientation distribution of fibers is not sensitive to the variation of obstacles. The initial orientation of fiber significantly affect the fiber orientation in the upstream channel, while has almost not effect on the orientation of fiber in the downstream channel. Further more, the higher of stokes number and lower fiber aspect ratio make the fiber aligned along the flow direction better. However, the velocity gradient of flow has a great effect on the distribution of fiber orientation.