Recent CFD developments for filter element simulations
Nowadays Computational Fluid Dynamics (CFD) simulations are often used in studying various filtration processes and in the design of filter elements. Algorithms and software for CFD simulations of filtration processes earlier were presented by Fraunhofer ITWM, see, e.g., (1,2). Some algorithmic aspects of our software tool, SuFiS®, are discussed in (3) . The current talk discusses three advanced recent developments. The first one is the subgrid resolution approach, the second one is computer simulation of the efficiency test, and the third one is the interaction of .fluid with deformable filtration media. The subgrid resolution is a challenging approach, which belongs to the class of variational multiscale methoids. More precisely, if some details of the filtration medium or of the filter element geometry are too fine to be resolved by the computational grid, they can be effectively accounted for by solving auxiliary problem on the proper grid cells, and modifying the coefficients of the Navier-Stokes-Brinkman equation there. In this approach, additional care is taken so that the upscaled coefficients for the Navier- Stokes-Brinkman approximate the pressure drop of the unresolved fine scale geometrical details accurately enough. A challenge in studying filtration processes is the CFD simulation of efficiency tests. We combine parameter identification from measurements carried out on a simplified filter element, with CFD simulation, in order to predict filter efficiency for newly designed filter elements. The parameter identification is based on solving auxiliary problems for one dimensional filtration process. The developed software tool is not only used to evaluate the efficiency of the manufactured filters, but also assists tremendously the engineers in designing new filter elements and selecting the proper filtering medium. It is known that the filtering medium may be subject to large deformations due to the fluid pressure. To account for such deformations, as well as for the back influence of the changed filter medium geometry on the flow within a filter element, Fraunhofer ITWM is developing software for poroelastic plates and shells, and for their interaction with the fluid to be filtrated.