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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

人体肺的气道由一个非常复杂的分支管网络组成。在每个支气管，气道重复分支，其平均直径和长度递减。在气道的末端，存在着许多将二氧化碳交换为氧气的肺泡。对于导电气道中的气体输运，人们做了大量的研究。然而，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，作者揭示了在人体肺系统的传导气道中发生的双向轴向气体交换现象是由流动分离区“产生-消失”引起的“捕获-释放”机制控制的。为了进一步研究真实人体肺中发生的现象，在二维测试切片的基础上，又新建了三维测试切片。对多代支管网络内往复流动进行了流动可视化实验和数值分析。实验结果表明：(1)即使在三维试验段，“困放”机制也发挥了重要作用。(2)在三维试验段中，祖管内的非对称流动导致轴向传质速度随路径的不同而不同。(3)轴向质量输运的最快路径取决于连续分支之间的旋转角度所决定的几何构型。在数值分析中，采用有限体积法，计算了具有三种不同分支角度的二维分支情况。在数值结果中，观察了流分离泡的大小与轴向质量输运的关系。这种关系不是单调的，因此必然存在一个最优分支角。通过对流场的详细考察，发现流分离泡对质量输运的增强有两种作用：一是“截留-释放”效应，二是通过减小流动通道的横截面积使流体加速。少