Realistic air filter media performance simulation. Part II: Beyond finite-volume computational fluid dynamics procedures

One form of numerical simulation of flow and particle capture by air filter media sees gases as continuous fluids, influenced by the macro-properties viscosity, density, and pressure. The alternate approach treats gases as atoms or molecules in random motion, impacting their own kind and solid surfaces on a micro-scale. The appropriate form for analysis of flow through a given filter medium at a given operating condition depends on the gas condition and the Knudsen number (Kn) of the finest fibers in the filter medium simulated. Continuum, macro-scale methods may be usable for media with individual fiber Kn as high as 0.01. Part I of this article discussed simulations of air filter media performance, where all fibers are in the continuum flow regime and the Navier–Stokes equation with a finite-volume solution is applicable. Here, Part II discusses filter media performance simulation by computational approaches other than numerical solutions of the Navier–Stokes equation. These include use of the Burnett, super-Burnett, and Grad moment equations; lattice Boltzmann and direct simulation Monte Carlo methods; and the molecular dynamics, boundary singularity, and boundary element methods.