Direct numerical simulation of cake formation during filtration with woven fabrics

Abstract

For surface filtration processes with woven fabrics as filter medium, the filter resistance and the structure of the first particle layers on the surface of the filter medium are important characteristics. First experimental results of Rushton (1970) indicated the existing interrelationships between the interference resistance and the structure of a filter medium. However, despite extensive investigations on the surface filtration, the mechanisms of the first layer formation and cake growth depending on the microstructure of the filter medium are still not well understood. In this study, direct numerical simulation of the flow and the particle deposition on weave models were performed with the in-house developed program DNSlab to describe the influence of the first particle layer on the flow resistance. In this approach, the differential Stokes equations were numerically solved with the finite-difference method. Three-dimensional geometric models of fabrics were generated by entering the parameters of the woven structures. The particle flow until deposition was calculated by solving the Newtońs equation of motion. The simulations consider that deposited particles influence the fluid by recalculation of the flow after each deposition of a particle. The results show that the flow through resistance increases abruptly once all pores are blocked and that the resistance depends on the ratio of pore size to particle size. Further, it could be shown that the use of twill weave reduces the flow resistance at filtration of spherical particles.