Numerical simulation of filtration processes in the flow-induced deformation of fibrous porous media by a three-dimensional two-way fluid–structure interaction scheme

Abstract

This study develops a numerical scheme to simulate three-dimensional two-way fluid–structure interaction (twFSI) problems capable of handling multiple simultaneous collision/contact (MSC) of a large number of flexible fibers. Our previous work of the twFSI scheme coupling the lattice Boltzmann method (LBM) as a fluid solver and the Cosserat rod model (CRM) as a structure solver is extended. To stably and efficiently calculate the collision/contact behaviors of numerous flexible fibers, the second-order extrapolation refilling method and the constrained-based collision model are implemented. The developed scheme (MSC-twFSI) is successfully validated in the experimental benchmark of flexible fiber collision/contact behaviors induced by airflows in a wind tunnel. The MSC-twFSI scheme is then applied to simulate the fluid flows through deformable nonwoven fabric geometry. In filtration processes through layers of fibrous materials such as face mask applications, the fluid flow induces a pressure distribution on individual fibers, resulting in deformation of each fiber and hence the overall fibrous porous structure is deformed. Therefore, we investigate the effect of the flow-induced deformation of fibrous porous media on the critical parameters of the filtration efficiency. They (porosity, compression ratio and permeability of the fibrous materials) are the key factors for designing filtration products. Fluid flows through deformable nonwoven fabrics, whose geometrical structures are close to realistic ones produced by the spunbonded lay-down process, are discussed under the actual air filtration environment of coughing. It is then found that (i) between the deformable and non-deformable fiber conditions, the maximum prediction difference for the permeability is 20.7%, (ii) the permeability difference comes from the anisotropic orientation of the fibers along the flow direction, and (iii) the effect of the flow-induced deformation approaches asymptotically ignorable below the porosity of around 0.83.