Approaches to Modeling Bed Drag in Pine Forest Litter for Wildland Fire Applications

Eric Mueller*, Michael Gallagher, Nicholas Skowronski, Rory M. Hadden

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Modeling flow in vegetative fuel beds is a key component in any detailed physics-based tool for simulating wildland fire dynamics. Current approaches for drag modeling, particularly those employed in multiphase Computational Fluid Dynamics (CFD) models, tend to take a relatively simple form and have been applied to a wide range of fuel struc-tures. The suitability of these approaches has not been rigorously tested for conditions which may be encountered in a wildland fire context. Here, we focus on beds of Pinus rigida nee-dle litter and undertake a two-part study to quantify the drag and evaluate the capabilities of a multiphase large eddy simulation CFD model, the NIST Fire Dynamics Simulator. In the first part, bed drag was measured in a wind tunnel under a range of conditions. The results were fit to a Forchheimer model, and the bed permeability was quantified. A tradi-tional approach employed in the multiphase formulation was compared to the parameterized Forchheimer equation, and was found to over-predict the drag by a factor of 1.2 to 2.5. In the second part, the development of a velocity profile above and within a discrete fuel layer was measured. Using the Forchheimer equation obtained in the first part of the study, the CFD model was able to replicate a qualitatively consistent velocity profile development. Within the fuel bed, the model appeared to under-predict the velocity magnitudes, which may be the result of unresolved pore-scale flow dynamics.
Original languageEnglish
Pages (from-to)1-24
Number of pages24
JournalTransport in Porous Media
Publication statusPublished - 25 Jun 2021

Keywords / Materials (for Non-textual outputs)

  • Wildland fires
  • CFD modeling
  • Vegetation
  • multiphase flow


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