1 Computer Models of Nonwoven Geometry and Filtration Simulation

A geometric model for the 3 dimensional structure of nonwoven was developed. It contains the porosity, fiber diameters and fiber anisotropy as parameters, and results in complex realizations of the media. Due to the use of a random number generator, no two realizations look alike albeit they all satisfy the requirements for porosity, fiber diameter distribution and fiber anisotropy within a prescribed tolerance. This is very similar to real nonwoven, where no two small samples ever look exactly the same. In these structures, the fluid flow and particle deposition are simulated. Initial pressure drop, filter efficiency and filter lifetime are quantities that are computed based on the nonwoven, the mean flow velocity and the particle size distribution. Additionally, electric charges, adhesion forces and in case of very small particles, diffusion may play a role. With this simulation chain from nonwoven geometry to filtration properties, ultimately the virtual material design of nonwoven will become feasible: For a given filtration application, an optimal, possibly graded nonwoven is sought by an automated computer simulation that finds the best nonwoven parameters. Of course, also other than filtration properties can be simulated, current interests lie in deformations, acoustic absorption and effective strength