Date of Award
Doctor of Philosophy (PhD)
Materials Science and Engineering
Dr. Konstantin G. Kornev
Dr. Olga Kuksenok
Dr. Philip J. Brown
Dr. Igor Luzinov
Nonwoven fibrous materials represent a platform of flexible material substrates. Nonwovens are widely used in the production of napkins, paper, filters, wound covers and face masks. In addition, for many applications, nonwoven materials interact with fluids. For example, in filtration applications, nonwoven materials are used to clean fluids containing solid particles or emulsified droplets. The filtration performance is affected not only by the geometrical arrangement of fibers in non-woven materials but also wettability of fibers. Understanding the transport properties of nonwoven materials and interactions between the dispersed droplets and solid substrate is crucial for the design and optimization of filter media. The present work is focused on: (1) obtaining pore space information from 3D structure in nonwoven media and 2) predicting the liquid transport properties in fibrous materials, including permeability and tortuosity (3) investigating droplet morphology on fibers.
Chapters 1-3 provide the basis of fiber-liquid interactions and introduce the lattice Boltzmann method (LBM). Chapter 4 deals with characterization of microstructures generated from 3D reconstructed plywood and random oriented fibrous media. An algorithm based on watershed segmentation is utilized to extract pore network information including: pore diameter, throat diameter and connectivity. The effect of fiber overlapping arrangements, fiber radius and porosity on the pore space morphology was explored by statistical pore-network analysis. A thorough analysis of the correlation between effective geometrical properties and mean pore size, demonstrated that randomness on microscopic level can have a significant effect on the macroscopic properties of the fibrous media.
In Chapter 5, simulations on pore-scale single phase fluid flow through fibrous media using the lattice Boltzmann method were performed. From the simulated flow field, permeability and tortuosity of nonwoven fibrous materials can be evaluated over a wide range of porosity 0.1 < φ < 0.9. The validity of Darcy’s law which describes the flow behavior through a porous medium was confirmed in the studied porosity regime. The simulation results were used to test the accuracy of semi-empirical scaling relations, that enabled predictions in trans-plane permeability and tortuosity based on porosity and specific surface area.
Chapter 6 deals with the wetting and capillarity effects of droplets deposited on a single fiber. A multicomponent pseudopotential lattice Boltzmann model was applied to study the interface dynamics of droplets and wetting/dewetting behavior. By adopting different initial droplet configurations, we studied the stability of barrel-shaped and clam-shell droplets on a single fiber for contact angles ranging from 10° to 68°. The simulated barrel drop profile was validated with experimental results. The morphology diagram established from simulations showed that both barrel and clam-shell configurations are stable in coexistence.
Dr. Ulf Schiller introduced me to the LBM, and guided my research described in Chapter 3-5. These chapters are based on publications [1, 2, 3], but significantly modified to include additional materials that has never been published. Chapter 6 has been developed to explain recent experimental results obtained in Dr. Kornev’s group. The developed simulation protocol revealed new physics related to the classical problem of fiber-drop interactions and a new diagram of morphological transitions of droplets on fibers was determined. The numerical simulations and data analysis were carried out on Palmetto high-performance computing (HPC) cluster.
Wang, Fang, "Computational Characterization of Nonwoven Fibrous Materials: Transport and Wetting Properties" (2022). All Dissertations. 3078.