Modeling tortuosity in fibrous porous media using computational fluid dynamics

Tortuosity factor is often used to characterize the structure of the pore volume in fibrous porous media. This work involves the determination of tortuosity using computational fluid dynamic (CFD) simulation and particle tracking analysis. A new method has been adopted to generate 3-D geometry for modeling fibrous porous structures using ANSYSRTM Parametric Design Language (APDL). Computation fluid dynamics has been used to simulate permeability of modeled 3-D fiberweb structures. The simulated permeability results are in good agreement with the models proposed by other authors. The experimental results were found to be slightly higher compared to simulated results and existing models due to the layered configuration of the samples. Permeability is found to be significantly influenced by fiber diameter, and porosity as well as fiberweb thickness. The relationship between air permeability and fiberweb thickness has been used to develop an indirect method for determination of tortuosity factor. Tortuosity factor has also been determined using a more direct method involving CFD simulation and Particle Tracking analysis. Different models established using the direct and indirect methods of determination show that tortuosity is significantly influenced by porosity, fiber diameter and fiberweb thickness, whereas the models available in the literature express tortuosity as a function of porosity only.