Simulation of impaction filtration by a porous filter

L. Ghazaryan, D.J. Lopez Penha, B.J. Geurts, S. Stolz, C. Winkelmann

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Abstract

We present a new numerical approach for estimating filtration through porous media from first principles. We numerically simulate particle motion as arises in a carrier gas flow. The filtration we look at occurs due to impaction of particles with obstructing surfaces that are contained in the solid filter. We consider the case when the motion of particles is governed by linear Stokes-drag, which is characterized by the particle relaxation time. The gas-particle interaction is modeled by using the Eulerian-Lagrangian approach and one-way coupling of the phases. In this case the carrier flow drags along the particles, without being affected by the motion of the particles. The gas flow is governed by Navier-Stokes equations for incompressible fluids and is calculated numerically using finite-volume discretization that is based on an energy conserving skew-symmetric discretization. We apply an immersed boundary (IB) method to capture the detailed flow in the porous filter, in which we explicitly incorporate flow around all small-scale features that make up the inner structure of the porous filter. To validate and develop our method we consider a porous medium composed of a staggered arrangement of square rods in 3D, which was already extensively considered in the literature for flow computation. This is a stepping-stone case on the way of simulating filtration of aerosol particles in complex, realistic filters. Based on results of our simulations we investigate the decay of the number of particles as a function of time. We focus on the dependence of the decay-rate on the Reynolds number of the gas and the inertial effects of the particles. For a range of particle relaxation times we observe a strong influence of the Reynolds number on filtration rate. A non-monotonic dependence of the filtration efficiency on Stokes number at different flow conditions is observed, hinting at qualitative differences in the motion of the aerosol ensemble through the structured filter.

Original languageEnglish
Title of host publicationPorous Media and Its Applications in Science, Engineering, and Industry - Third International Conference
EditorsK. Vafai
PublisherAmerican Institute of Physics
Pages129-134
Number of pages6
ISBN (Print)978-0-7354-0803-6
DOIs
Publication statusPublished - 20 Jul 2010
Event3rd International Conference on Porous Media and its Applications in Science, Engineering and Industry - Montecatini, Italy
Duration: 20 Jun 200925 Jun 2009

Publication series

NameAIP Conference Proceedings
Volume1254

Conference

Conference3rd International Conference on Porous Media and its Applications in Science, Engineering and Industry
CountryItaly
CityMontecatini
Period20/06/0925/06/09

Keywords

  • Computational fluid dynamics
  • Direct numerical simulation
  • Filtration efficiency
  • Immersed boundary method
  • Reynolds number
  • Stokes number
  • Structured porous media

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