We studied the effect of gravitational sedimentation on the dispersion of 0.5 and 1 micrometer-diameter particle boluses within a two-dimensional symmetric six-generation model of the human acinus. Boluses were introduced at the beginning of a 2-s inspiration immediately followed by a 4-s expiration, in normal gravity (1 G) and in the absence of gravity (0 G). The flow corresponded to a flow rate at the mouth of 500 ml/s. In 0 G, simulated dispersion (Hsim) was 16 ml for both particle sizes. In 1 G, Hsim was 71 and 242 ml for 0.5 and 1 micrometer-diameter particles, respectively, showing the effect of gravitational sedimentation. The difference between experimental data (J. Appl. Physiol. 86 (1999) 1402) and simulations was independent of particle size. This suggests that the residual dispersion was independent of the intrinsic properties of the particles and was more likely due to other mechanisms such as ventilation inhomogeneities, cardiogenic oscillations and alveolar wall motion.

中文翻译：

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重力沉降对人体腺泡中模拟气溶胶弥散的影响

我们研究了重力沉降对 0.5 和 1 微米直径粒子团在二维对称六代人腺泡模型中的分散的影响。在正常重力 (1 G) 和无重力 (0 G) 下，在 2 秒吸气开始后立即引入 4 秒呼气。流量对应于500ml/s的口处流速。在 0 G 下，两种粒径的模拟分散 (Hsim) 均为 16 ml。在 1 G 中，对于 0.5 和 1 微米直径的颗粒，Hsim 分别为 71 和 242 毫升，显示了重力沉降的影响。实验数据 (J. Appl. Physiol. 86 (1999) 1402) 和模拟之间的差异与粒径无关。