Lagrangian transport properties of pulmonary interfacial flows
Lagrangian transport properties of pulmonary interfacial flows
复制标题
肺界面流的拉格朗日传输特性
DOI：
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发表时间：
2011
影响因子：
3.7
通讯作者：
D. Gaver
中科院分区：
文献类型：
--
作者：
Bradford J. Smith;Sarah R. Lukens;E. Yamaguchi;D. Gaver
摘要 以气道液体闭塞和肺表面活性物质缺乏为特征的疾病状态，如呼吸窘迫综合征，具有很高的死亡率。了解气道重新开放的机制，特别是涉及表面活性剂转运的机制，可能会提供一种通过优化机械通气波形来提高患者生存率的途径。我们将闭塞气道建模为充满液体的刚性管，其中流体相被空气指所取代，空气以平均速度分量和正弦速度分量传播。采用有限时间李雅普诺夫指数 (FTLE) 场来分析对流传输特性，同时考虑拉格朗日相干结构 (LCS) 及其对传输的影响。这些技术的拉格朗日视角揭示了通过观察欧拉测量不容易明显看出的流动特征。这些分析技术适用于通过边界元法计算确定的无表面活性剂速度场，并通过微粒图像测速法（$\ensuremath{\mu} $ -PIV）进行实验测量。我们发现 LCS 将流体分为两种状态，一种是向上游平流输送（进入薄残膜），另一种是在前进的气泡之前向下游流动。在较高的振荡频率下，直接源自 LCS 内部的颗粒在气液界面处经历较长的停留时间，这可能有利于表面活性剂的传输。在高频下，可以识别出混合良好的吸引子区域；该体积的流体沿着界面循环流动并进入本体流体。拉格朗日分析应用于在大量流体中使用 0.01 mg ml−1 临床肺表面活性剂 Infasurf 测量的速度数据，证明了相对于无表面活性剂系统的流场变化，这在欧拉框架中不可见。
Abstract Disease states characterized by airway fluid occlusion and pulmonary surfactant insufficiency, such as respiratory distress syndrome, have a high mortality rate. Understanding the mechanics of airway reopening, particularly involving surfactant transport, may provide an avenue to increase patient survival via optimized mechanical ventilation waveforms. We model the occluded airway as a liquid-filled rigid tube with the fluid phase displaced by a finger of air that propagates with both mean and sinusoidal velocity components. Finite-time Lyapunov exponent (FTLE) fields are employed to analyse the convective transport characteristics, taking note of Lagrangian coherent structures (LCSs) and their effects on transport. The Lagrangian perspective of these techniques reveals flow characteristics that are not readily apparent by observing Eulerian measures. These analysis techniques are applied to surfactant-free velocity fields determined computationally, with the boundary element method, and measured experimentally with micro particle image velocimetry ( $\ensuremath{\mu} $ -PIV). We find that the LCS divides the fluid into two regimes, one advected upstream (into the thin residual film) and the other downstream ahead of the advancing bubble. At higher oscillatory frequencies particles originating immediately inside the LCS experience long residence times at the air–liquid interface, which may be conducive to surfactant transport. At high frequencies a well-mixed attractor region is identified; this volume of fluid cyclically travels along the interface and into the bulk fluid. The Lagrangian analysis is applied to velocity data measured with 0.01 mg ml−1 of the clinical pulmonary surfactant Infasurf in the bulk fluid, demonstrating flow field modifications with respect to the surfactant-free system that were not visible in the Eulerian frame.
影响因子：
158.5
作者：
Rubenfeld, GD;Caldwell, E;Hudson, LD
通讯作者：
Hudson, LD
影响因子：
3.3
作者：
GAVER, DP;SAMSEL, RW;SOLWAY, J
通讯作者：
SOLWAY, J
影响因子：
8.6
作者：
Drescher K;Leptos KC;Tuval I;Ishikawa T;Pedley TJ;Goldstein RE
通讯作者：
Goldstein RE