A lot of research has been done to explore flow laws in a fibrous network. Stylianopoluos et al. [
6] used finite-element simulation to study permeability in fibrous material with isotropic and oriented fiber arrangements. Specifically, aligned networks were generated by selecting directional vectors from an anisotropic distribution and the impact of porosity on permeability was discussed. Nabovati et al. [
7] reconstructed fibrous media with straight cylinders of random arrangement and studied the permeability using the lattice Boltzmann method. Structural features involving curvature and aspect ratio of fibers on the permeability were also determined. The virtual geometric models [
6,
7], however, were constructed without sufficient verification by comparing to the real structures. Recently, X-ray tomography has rapidly developed and has been widely applied to material science, especially in the non-destructive reconstruction of porous materials, such as granular materials [
8], metal foams [
9], and fiber materials [
10]. Pradeep et al. [
11] converted 3D tomography images into pore network modeling [
12,
13] which was composed of pores and connecting pore throats and in which a mass balance was imposed at each pore, and the flow through the pore throats was approximated. Using 3D image data, Koviu et al. [
15] studied the permeability of plastic felt and hand-sheet paper. In this work, simulation results (using the lattice Boltzmann method and the finite-difference method) were compared with experimental results. The lattice Boltzmann method was performed on 3D tomographic images directly. To generate grid data for the finite-difference method from 3D images, the Geodict package (
http://www.geodict.com) was used [
5,
14]. Similar work was reported by Brun et al. [
16], in which flow laws were explored in metal foams. The reconstructed faceted geometries in STereo Lithography (STL) file format were volumetrically meshed into the continuous fluid domain and simulation was conducted using a common Computational Fluid Dynamics (CFD) software package. However, meshing disordered 3D geometries from STL data are usually very time-consuming as it requires extensive computational resources [
17]. Therefore, it is promising to develop an alternative virtual modeling method and fit the model to the real geometrical characteristics that can be obtained through morphological exploration from 3D tomographic images. Such virtual models are usually constructed with Computer-Aided Design (CAD) packages in which the models can be exported using file formats supported by the most commercial CFD software, such as Fluent Inc. In a recent study, Heitzmann et al. [
18] investigated the permeability of anisotropic sintered metallic fiber structures through CFD simulation. In this study, the anisotropy tensor was applied for geometric model fitting and the analytical method by Shou et al. [
19] was used to obtain the best results. In this way, optimal structure achieving the best performance can be determined by slightly modifying the geometric model through altering the controllable structural parameters and investigating their corresponding performances through simulation experiments.
It should be noted that that, in most publications, numerical results of the transport property are investigated at creep flow (low Reynolds number). Unfortunately, due to technical limitations [
17,
33], the experimental settings are usually performed at higher flow rates at which the impact of inertial effects cannot be neglected. However, the numerical results of transport properties of porous material at higher flow rates are seldom reported [
16]. To fill these gaps, this research aims to develop a method for constructing virtual models which can support effective simulation-based study of transport properties at high flow rates.