Numerical study of high-frequency oscillatory air flow and convective mixing in a CT-based human airway model.
Numerical study of high-frequency oscillatory air flow and convective mixing in a CT-based human airway model.
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DOI：
10.1007/s10439-010-0110-7
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发表时间：
2010-12
影响因子：
3.8
通讯作者：
Lin, Ching-Long
中科院分区：
文献类型：
--
作者：
Choi, Jiwoong;Xia, Guohua;Tawhai, Merryn H.;Hoffman, Eric A.;Lin, Ching-Long
高频振荡通气（HFOV）被认为是一种有效和安全的呼吸技术，用于新生儿和急性呼吸窘迫综合征患者。HFOV具有与正常呼吸生理学非常不同的特征，具有小得多的潮气量和较高的呼吸频率。在这项工作中，高频振荡流的研究，使用计算流体动力学（CFD）分析在三个不同的几何模型，越来越复杂：直管，单分叉管模型，和计算机断层扫描（CT）为基础的人体气道模型多达七代。我们的目的是了解逆流现象在流动逆转和对流混合在这些模型中使用不同的频率和雷诺数的正弦波形的作用。通过拉伸速率分析来量化混合。在直管模型中，与相反的流体流的同轴逆流形成周围的流动逆转，同意分析Womersley解决方案。然而，逆流在循环结束时不产生净对流混合。在单分叉模型中，在高Re下的逆流在呼气（吸气）末时在父（子）分支中被二次涡干预，导致不可逆的混合过程。对于基于CT的气道模型，考虑三种情况，包括正常呼吸情况、高频正常Re情况和HFOV情况。在高频正Re情况下，逆流结构比HFOV情况更明显。计算了两个呼吸周期结束时和流动逆转附近的瞬时和时间平均拉伸率。结果表明，逆流对混合的贡献约为20%。
High frequency oscillatory ventilation (HFOV) is considered an efficient and safe respiratory technique to ventilate neonates and patients with acute respiratory distress syndrome. HFOV has very different characteristics from normal breathing physiology, with a much smaller tidal volume and a higher breathing frequency. In this work, the high frequency oscillatory flow is studied using a computational fluid dynamics (CFD) analysis in three different geometrical models with increasing complexity: a straight tube, a single-bifurcation tube model, and a computed-tomography (CT)-based human airway model of up to seven generations. We aim to understand the counter-flow phenomenon at flow reversal and its role in convective mixing in these models using sinusoidal waveforms of different frequencies and Reynolds numbers. Mixing is quantified by the stretch rate analysis. In the straight-tube model, coaxial counter flow with opposing fluid streams is formed around flow reversal, agreeing with an analytical Womersley solution. However, counter flow yields no net convective mixing at end cycle. In the single-bifurcation model, counter flow at high Re is intervened with secondary vortices in the parent (child) branch at end expiration (inspiration), resulting in an irreversible mixing process. For the CT-based airway model three cases are considered, consisting of the normal breathing case, the high-frequency-normal-Re case, and the HFOV case. The counter-flow structure is more evident in the high-frequency-normal-Re case than the HFOV case. The instantaneous and time-averaged stretch rates at the end of two breathing cycles and in the vicinity of flow reversal are computed. It is found that counter flow contributes about 20% to mixing in HFOV.
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影响因子：
4.6
作者：
Choi, Jiwoong;Tawhai, Merryn H.;Lin, Ching-Long
通讯作者：
Lin, Ching-Long
影响因子：
4.7
作者：
Mackley, MR;Saraiva, RMCN
通讯作者：
Saraiva, RMCN
DOI：
10.1164/rccm.2108052
发表时间：
2002-09-15
影响因子：
24.7
作者：
Derdak, S;Mehta, S;Granton, J
通讯作者：
Granton, J
影响因子：
3.8
作者：
Heraty, Kevin B.;Laffey, John G.;Quinlan, Nathan J.
通讯作者：
Quinlan, Nathan J.
影响因子：
8.6
作者：
Majumdar, A;Alencar, AM;Suki, B
通讯作者：
Suki, B