Computational fluid dynamics (CFD) was used to evaluate the contribution of secondary aspiration to human aspiration efficiency estimates using a humanoid model with realistic facial features. This study applied coefficient of restitution (CoR) values for working-aged human facial skin to the facial regions on the humanoid CFD model. Aspiration efficiencies for particles ranging from 7 to 116 μm were estimated for bounce (allowing for secondary aspiration) and no-bounce (CoR=0) simulations. Fluid simulations used the standard k-epsilon turbulence model over a range of test conditions: three freestream velocities, two breathing modes (mouth and nose breathing, using constant inhalation), three breathing velocities, and five orientations relative to the oncoming wind. Laminar particle trajectory simulations were used to examine inhaled particle transport and estimate aspiration efficiencies. Aspiration efficiency for the realistic CoR simulations, for both mouth- and nose-breathing, decreased with increasing particle size, with aspiration around 50% for 116 μm particles. For the CoR=0 simulations, aspiration decreased more rapidly with increasing particle size and approached zero for 116 μm compared to realistic CoR models (differences ranged from 0% to 80% over the particle sizes and velocity conditions). Differences in aspiration efficiency were larger with increasing particle size (>52 μm) and increased with decreasing freestream velocity and decreasing breathing rate. Secondary aspiration was more important when the humanoid faced the wind, but these contributions to overall aspiration estimates decreased as the humanoid rotated through 90°. There were minimal differences in aspiration between uniform CoR values of 0.5, 0.8, 1.0 and realistic regionally-applied CoR values, indicating differences between mannequin surfaces and between mannequin and human skin will have negligible effect on aspiration for facing-the-wind orientation.

中文翻译：

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二次吸入对人体吸入效率的影响

计算流体动力学 (CFD) 用于使用具有逼真面部特征的人形模型来评估二次吸入对人类吸入效率估计的贡献。本研究将工作年龄人类面部皮肤的恢复系数 (CoR) 值应用于人形 CFD 模型上的面部区域。对于反弹（允许二次吸入）和非反弹（CoR = 0）模拟，估计了 7 至 116 μm 颗粒的吸入效率。流体模拟在一系列测试条件下使用标准 k-epsilon 湍流模型：三种自由流速度、两种呼吸模式（口呼吸和鼻呼吸，使用恒定吸入）、三种呼吸速度以及相对于迎面而来的风的五个方向。层流粒子轨迹模拟用于检查吸入的粒子传输和估计吸入效率。真实 CoR 模拟的吸入效率（口呼吸和鼻呼吸）随着粒径的增加而降低，116 μm 颗粒的吸入效率约为 50%。对于 CoR=0 模拟，与实际 CoR 模型相比，吸入随着颗粒尺寸的增加而下降得更快，并且在 116 μm 时接近零（颗粒尺寸和速度条件的差异范围为 0% 到 80%）。吸入效率的差异随着粒径的增加（> 52 μm）而变大，并随着自由流速度的降低和呼吸频率的降低而增加。当人形面对风时，二次吸入更重要，但随着类人机器人旋转 90 度，这些对总体吸入估计的​​贡献减少了。0.5、0.8、1.0 的统一 CoR 值与实际区域应用的 CoR 值之间的愿望差异很小，表明人体模型表面之间以及人体模型与人体皮肤之间的差异对迎风方向的愿望影响可以忽略不计。