Ahmed Nurye Oumer

Numerical prediction of flow induced fibers orientation in injection molded polymer composites

Since the filling stage of injection molding process has important effect on the determination of the orientation state of the fibers, accurate analysis of the flow field for the mold filling stage becomes a necessity. The aim of the paper is to characterize the flow induced orientation state of short fibers in injection molding cavities. A dog-bone shaped model is considered for the simulation and experiment. The numerical model for determination of the fibers orientation during mold-filling stage of injection molding process was solved using Computational Fluid Dynamics (CFD) software called MoldFlow. Both the simulation and experimental results showed that two different regions (or three layers of orientation structures) across the thickness of the specimen could be found: a shell region which is near to the mold cavity wall, and a core region at the middle of the cross section. The simulation results support the experimental observations that for thin plates the probability of fiber alignment to the flow direction near the mold cavity walls is high but low at the core region. It is apparent that the results of this study could assist in decisions regarding short fiber reinforced polymer composites.

Numerical and Qualitative Analysis of a Single Particle Behavior in a Shear Driven Flow in Equilateral Triangular Cavity

Intesive research works have been done on solid particle flows for the past decades. However, prediction of accurate relationship between the particle and the surrounding fluid is still challenging. This study focuses on the experimental and numerical study of behavior of a particle flow in a lid-driven cavity of equilateral triangular shape. Numerical analysis was done using Finite Difference Method (FDM) with stream function vorticity approach. The center location of the fluid flow was treated assumed to be the particle motion. To check the validaty of the numerical results, experiment was done. The particle and fluid used for the experiment were water and silk, respectively. The particle is considered to be slightly buoyant towards water. In the experiment the fluid flow was based on horizontal translating motion where the particle was initially at rest at the bottom wall of the cavity. The fluid flow speed is set to laminar flow with Reynolds Number, Re = 0 to 1000. It was found that the silk particle moved to the preferential path of the primary vortex at equivalent time of 13 seconds. Generally, the experimetal and numerical results for the streamlines were in good agreement.