Carousel effect in alveolar models.
Carousel effect in alveolar models.
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肺泡模型中的旋转木马效应。
DOI：
10.1115/1.2903429
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Hydon,PE
中科院分区：
文献类型：
--
作者：
Laine-Pearson,FE;Hydon,PE
过去十年的实验工作表明，肺泡中的再循环大大增加了颗粒的运输。我们以前已经表明，对于非扩散的被动粒子，这可以理解与莫法特的著名的角流模型的帮助。没有壁面运动，被动粒子以规则的方式再循环，不存在混沌;然而，壁面运动产生广泛的混沌流。气溶胶通常不遵循这种流动，因为它们与流体颗粒有根本的不同。在这里，我们构建了一个简单的模型来研究扩散粒子在回流的存在。我们假设所有粒子都是被动的，也就是说，它们不会显著地改变底层流。特别地，我们考虑具有高Péclet数的粒子，忽略惯性效应。我们修改拉格朗日系统的角落涡，以适应扩散粒子。粒子输运由朗之万方程控制。扩散粒子系综的跟踪数值积分。我们表明，通过一种机制，我们称之为“旋转木马效应”足够强大的底层再循环增强扩散粒子的运输。然而，当接近拐角时，再循环强度迅速降低，有利于扩散运动。在远离拐角顶点的地方，再循环占主导地位。对于真实的肺泡，该模型表明，足够强的再循环可以通过转盘效应增强扩散颗粒的运输。
Experimental work over the past decade has shown that recirculation in alveoli substantially increases the transport of particles. We have previously shown that, for nondiffusing passive particles, this can be understood with the aid of Moffatt’s famous corner flow model. Without wall motion, passive particles recirculate in a regular fashion and no chaos exists; however, wall motion produces extensive chaotic flow. Aerosols typically do not follow this flow as they are fundamentally different from fluid particles. Here, we construct a simple model to study diffusing particles in the presence of recirculation. We assume that all particles are passive, that is to say that they do not significantly alter the underlying flow. In particular, we consider particles with high Péclet number and neglect inertial effects. We modify the Lagrangian system for corner eddies to accommodate diffusing particles. Particle transport is governed by Langevin equations. Ensembles of diffusing particles are tracked by numerical integration. We show that transport of diffusing particles is enhanced by sufficiently strong underlying recirculation through a mechanism that we call the “carousel effect.” However, as the corner is approached, the recirculation rapidly decreases in intensity, favoring motion by diffusion. Far from the corner’s apex, recirculation dominates. For real alveoli, the model indicates that sufficiently strong recirculation can enhance transport of diffusing particles through the carousel effect.