Modelling the flow transition at the porous fluid interface of pleated filter elements

F. Keller*, D. Riesterer, M. Lehmann, Mann+Hummel GmbH, Germany

CFD simulation of pleated filter elements is a multiscale challenge. For predicting the pressure drop accurately it is necessary to understand the flow behavior from micro- to macroscale. Due to limited hardware capacity it is not possible to simulate a filter pleat with fully resolved filter media at microscale level. Thus, simplified models for the filter media are needed to reduce the complexity of the problem. Especially the correct flow behavior at the interface between porous media and the free flow domain has to be taken into account.

In standard CFD simulations of pleated filter elements the interface between the free flow domain and the porous media is modelled as a sharp interface. Further the filter media is only characterized by its thickness as well as by its permeability, which is assumed to be constant and isotropic. However it is known from microstructure simulations that due to the fibrous structure of the media the flow field is showing a slip velocity at the interface of the porous media. The slip velocity is thereby dependent on the microstructure at the interface as well as on the channel width of the pleat.

In this work we present a new multiscale approach which includes a locally resolved permeability distribution in the porous media as well as a differentiation of the permeability values in tangential and normal direction. The implementation was done in the commercial CFD software ANSYS FLUENT. We will investigate in detail the advantages of the new models and compare it to previous results obtained from standard models. In addition we present a newly developed analytical 1D model, which is an extension of the well-known Caesar and Schroth model...

Session: F6 - Filter Media - Numerical Simulation of Stressed Filter Elements
Day: 13 October 2016
Time: 14:45 - 16:00 h

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