Effects of Fiber Orientation on Flow Properties of Fibrous Porous Structures at Moderate Reynolds Number

In this study, effects of porosity and fiber orientation on the viscous permeability and Forchheimer coefficient of mono-dispersed fibers are investigated. The porous material is represented by a unit cell which is assumed to be repeated throughout the medium. Based on the orientation of the fibers in the space, fibrous media are divided into three categories: 1D, 2D, and 3D structures. Parallel and transverse flow through square arrangements of 1D fibers, simple 2D mats, and 3D simple cubic structures are solved numerically over a wide range of porosities, 0.35 < ε < 0.95 and Reynolds numbers 0.01 < Re < 200. The results are used to calculate permeability and the inertial coefficient of the solid matrices. An experimental study is performed; the flow coefficients of three different ordered tube banks in the moderate range of Reynolds number, 0.001 < Re < 15, are determined. The numerical results are successfully compared with the present and the existing experimental data in the literature. The results suggest that permeability and Forchheimer coefficient are functions of porosity and fiber orientation. A comparison of the experimental and numerical results with Ergun equation reveals that this equation is not suitable for highly porous materials. As such, new, accurate correlations are proposed for determining the Forchheimer coefficient in fibrous media.