Effect of 3D fiber orientation on permeability of realistic fibrous porous networks

The development of scientifically based fibrous porous networks has been gaining momentum due to their potential advantages in a wide spectrum of end-uses. Flow of fluid through fibrous networks is the determining factor in the engineering of these materials for applications in various manufacturing and process industries. Precise definition of transport properties of fibrous porous networks necessitates greater understanding of their internal structure at the micro-scale. To this end, in this work an X-ray micro-computed tomography-based CFD simulation methodology was developed. Realistic 3D images of fibrous networks were prepared using sets with various degrees of alignment including nearly isotropic, nearly layered and moderately aligned networks. The in-plane and transverse permeability of such structures were obtained by solving the Stokes equations. The presentation of the results for each type of fibrous network structure and flow configuration is preceded by brief outlines of the pertinent literature works, and followed by a discussion on the performance of the micro-computed tomography-based method and the literature models. It was established that simultaneous application of X-ray micro-computed tomography and CFD techniques merits the in depth understanding of the microscopic fluid flow phenomenon in respected models of fibrous porous structures and its subsequent role on the performance of a fibrous porous network. Results indicated that not only the solid volume fraction, but also the 3D orientation of fibers in fibrous networks affects the permeability.