Flow modeling in dual scale porous media

The main focus of this dissertation is the study of flow of a viscous liquid in dual scale porous media as encountered during the mold filling process in resin transfer molding (RTM). This type of porous media is created due to the use of woven fiber mats in this process to manufacture polymer composites.;The single phase flow through dual scale porous media is explored with the help of unit cells where the flow in inter-tow and intra-tow spaces is modeled by Stokes and Brinkman equations respectively. Analytical and numerical models for the permeability are developed for the principle directions. Parametric studies reveal that the relative significance of the flow inside the tows vis-a-vis the flow outside the tows for the computation of permeability depends upon the spacing between the tows and their permeability. Clustering of fibers of the fibrous porous media is shown to increase its permeability.;An experimental investigation of the capillary pressure driven flow across a bank of fibers is conducted in order to model the flow of resin inside the tows. Two separate models based on Darcy's law are proposed to describe the wicking process and, along with the Washburn's equation, are found to agree well with the experimental results.;The unsaturated flow through a 1-D dual scale porous medium is modeled as the flow of a viscous liquid into an aligned array of inter-tow regions flanked by intra-tow spaces. Order of magnitude analysis of different terms in the integral mass balance equation leads to the creation of a sink term in the equation of continuity which is further studied with the help of two simple cases. The unsaturated flows is classified into developing and fully developed flows and the important parameters are identified. Numerical simulation of the isothermal mold filling process in dual scale porous media is accomplished next where a mold filling simulation based upon finite element method/control volume (FEM/CV) method is adapted to model the dual scale flows. Different types of flows encountered in RTM are studied using this simulation and the effect of important parameters is investigated.;Finally, the creation and migration of voids in 1 - D RTM mold is modeled as the Buckley-Leverett type of flow through a porous medium and is found to agree favourably with the reported experimental observations.