A simple numerical method to simulate the flow through filter media: Investigation of different fibre allocation algorithms

Abstract

Flow patterns and pressure-drop through three fine-fibre air filter media were simulated using the lattice Boltzmann method. The geometry for the flow domain was two-dimensional, with fibres having truncated log-normal diameter distributions matching SEM photograph measurements on the actual media. The influence of the strategy in positioning the fibres inside the computational domain on the pressure drop of the filter media was investigated. Two different schemes were proposed to position the fibres into a cross section of the filter medium: a random distribution algorithm and the Mitchell's best candidate algorithm. Furthermore, no-slip and free-slip boundary conditions were tested for the fluid-fibre interaction. The comparison between numerical and experimental data shows that the random allocation of fibres better predicted the filter media behaviour. Simulated data suggest that the free-slip boundary condition must be used when studying the interaction of the fluid with small fibres similar to the size of the fibres used in this study. This study allowed the development of a simple strategy to estimate the pressure drop of a filter medium by having little information of its physical structure, such as solid fraction and diameter distribution.