Gas Exchange Mechanism in Conducting Airways of Human Lung

人肺气道传导的气体交换机制

基本信息

批准号：
13450080
负责人：
MOCHIZUKI Sadanari
金额：
$ 8.7万
依托单位：
Tokyo University of Agriculture and Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13450080/
关键词：
Reciprocating Flow Branching Tube Flow Separation Mass Transport Flow Visualization Finite volume Method

项目摘要

The airway of the human lung consists of a very complicated branching tube network. At each bronchus, the airways repeat branching with their average diameter and the length decreasing. At the end of airways, numerous alveoli that exchange carbon dioxide for oxygen exist. As for the gas transport in the conducting airways, a lot of researches have been done. However, the mechanism how the fresh air, which was inhaled in the inspiration process, reaches alveoli is not known well yet. Recently, the authors revealed that bi-directional axial gas-exchange phenomenon occurring in the conducting airways of human lung system was governed by "trap-and-release" mechanism caused by "generation-and-extinction" of flow-separation regions.In order to further examine the phenomena occurring in the real human lung, three-dimensional test sections were newly constructed in addition to the two-dimensional one. Flow visualization experiments and numerical analysis in reciprocating flow inside a multi-ge … More neration branching-tube network were performed. In the experiments, the followings were revealed : (1) Even in the 3-D test section, "trap-and-release" mechanism played an important role. (2) In the 3-D test section, asymmetric flow in the ancestor tube results in the different axial mass transport speed depending on the path. (3) The fastest path concerning the axial mass transport changed depending on the geometric configuration decided by the rotation angle between the successive branches.In the numerical analysis, the finite volume method was used, and a two-dimensional branching case was computed with three different branching angles. In the numerical results, the relation between the size of the flow-separation bubble and axial mass transport was observed. The relation was not monotonic, and therefore there must be an optimal branching angle. By examining the flow field in detail, it was observed that the flow-separation bubble had two effects on the mass transport enhancement : the "trap-and-release" effect and the acceleration of the fluid bv reducing the cross-sectional area of the flow passaee. Less

人体肺部的气道由非常复杂的分支管网络组成，在每个支气管处，气道重复分支，其平均直径和长度逐渐减小。在气道末端，存在许多将二氧化碳交换为氧气的肺泡。对于传导气道中的气体输送，人们已经进行了大量的研究，但是，在吸气过程中吸入的新鲜空气如何到达肺泡的机制尚不清楚，最近，作者透露。人体肺系统传导气道中发生的轴向气体交换现象是由气流分离区的“生灭”引起的“困放”机制控制的。实验中，除了二维分支管网络内的往复流动的流动可视化实验和数值分析外，还新建了真实的人肺。追随者结果表明：（1）即使在3-D测试段中，“捕获-释放”机制也发挥了重要作用（2）在3-D测试段中，祖先管中的不对称流动导致了不同的轴向。 (3) 轴向质量传输的最快路径根据连续分支之间的旋转角度决定的几何构型而变化。在数值分析中，使用了有限体积方法，并采用了两种方法。维分支情况是用三种不同的方法计算的在数值结果中，观察到流动分离气泡的尺寸与轴向质量传递之间的关系不是单调的，因此必须存在最佳的分支角。据观察，流动分离气泡对传质增强有两个作用：“捕获和释放”效应和通过减少流动通道的横截面积来加速流体。