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 structures. 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 needle 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 traditional 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 1.2–2.5. 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.

模拟植物燃料床中的流动是用于模拟野火动力学的任何基于物理的详细工具的关键组成部分。当前的阻力建模方法，特别是用于多相计算流体动力学 (CFD) 模型的方法，往往采用相对简单的形式，并已应用于广泛的燃料结构。这些方法的适用性尚未针对在野火环境中可能遇到的条件进行严格测试。在这里，我们专注于松树的床针砂并进行了一项由两部分组成的研究，以量化阻力并评估多相大涡流模拟 CFD 模型（NIST 火灾动力学模拟器）的能力。在第一部分中，在一系列条件下的风洞中测量了床层阻力。结果符合 Forchheimer 模型，并对床渗透率进行了量化。将多相公式中采用的传统方法与参数化 Forchheimer 方程进行比较，发现其高估了 1.2-2.5 倍的阻力。在第二部分中，测量了离散燃料层上方和内部的速度分布的发展。使用在研究的第一部分中获得的 Forchheimer 方程，CFD 模型能够复制定性一致的速度剖面发展。在燃料床内，