CFD Investigation of Particle Inhalability in Low Windspeeds

描述（由申请人提供）：计算流体动力学（CFD）建模技术可用于检查污染物传输和估计个人暴露。这项工作提出了使用计算流体动力学来研究在低速环境中的颗粒吸入，典型的职业环境。这项工作的长期目标是提供指导，以制定一个国际性能标准，可吸入颗粒物采样器在室内使用时，几乎没有空气流动。现有的标准是从更大风速的实验中发展出来的，这可能会高估工人在室内环境中吸入的颗粒物数量。CFD方法允许模拟均匀的颗粒浓度场，使我们能够避免与大颗粒均匀悬浮相关的实验困难。最初的研究已经开发，验证和验证了一个单一的人形形式的计算机表示，以调查粒子吸入使用标准的k-k湍流模型在面对风的方向。这项研究将：（1）检查吸入效率估计对面部特征尺寸、湍流方程和反弹参数的敏感性，以量化吸入效率估计中的不确定性;（2）研究在除迎风方向之外的方向上的颗粒吸入，以了解方向和速度参数对人形形式的颗粒吸入的影响;（3）提出一种低速抽吸效率曲线，用于制定可吸入颗粒物采样器标准。这项工作支持接触评估方法诺拉优先研究领域。目前的问题是，使用现有的高速IPM标准收集的职业接触样本收集颗粒的效率大于工人可以吸入的。如果是这样的话，基于质量的暴露估计将高估个人的真实暴露。一旦将健康影响研究应用于这些接触估计，风险估计将基于高估的接触。这将导致风险评估实际上低估了工人接触的风险。这项研究将确定评估工作场所大颗粒物暴露的取样标准是否需要调整，以改善暴露和风险估计。

DESCRIPTION (provided by applicant): Computational fluid dynamics (CFD) modeling techniques can be used to examine contaminant transport and to estimate personal exposure. This work proposes to use CFD to investigate particle aspiration in low velocity environments, typical of the occupational environment. The long-term objective of this work is to provide guidance to the development of an international performance criterion for inhalable particle samplers when used indoors with little air movement. The existing criterion was developed from experiments in larger windspeeds, which may overestimate the amount of particles that are inhaled by a worker in an indoor setting. CFD methods allow the simulation of uniform particle concentration fields, allowing us to avoid the experimental difficulties associated with uniform suspension of large particles. Initial research has developed, validated, and verified a computer representation of a single humanoid form to investigate particle aspiration using the standard k-epsilon turbulence model in the facing-the-wind orientation. This research will: (1) examine the sensitivity of aspiration efficiency estimates to facial feature dimensions, turbulence equations, and bounce parameters to quantify uncertainty in aspiration efficiency estimates; (2) investigate particle aspiration at orientations other than facing-the-wind to understand the influences of orientation and velocity parameters on particle aspiration for a humaniod form; (3) to propose a low velocity aspiration efficiency curve for use in the development of an inhalable particle sampler criterion. This work supports the Exposure Assessment Methods NORA priority research area. There is current concern that occupational exposure samples collected using the existing high-velocity IPM criterion collects particles at efficiencies greater than what can be inhaled by workers. If so, mass-based exposure estimates will overestimate the true exposures of individuals. Once health effects studies are applied to these exposure estimates, risk estimates will be based on overestimated exposures. This will result in risk assessments that actually underestimate the risk of exposure to workers. This research will identify whether the sampling criterion to assess exposures to large particles in workplaces requires adjustment to improve exposure and risk estimates.