Reopening modes of a collapsed elasto-rigid channel
Reopening modes of a collapsed elasto-rigid channel
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塌陷弹刚性通道的重新打开模式
作者：
Lucie Ducloué;A. Hazel;A. Thompson;A. Juel
受强塌陷通道重开力学的启发，我们研究了空气手指在具有单一柔顺壁面的塌陷充油通道中的稳定传播。在之前的一项使用全顺应性弹性管的研究中，发现了一个“尖头”空气手指以高速和低压传播，如果临床上可以接触到这种手指，就有可能以最小的组织损伤快速重新打开高度塌陷的呼吸道(Heap&Juel Phys)。《流体》，第20卷(8)，2008年，081702)。然而，选择那个尖尖手指的机制仍然没有得到解释。在本文中，我们通过在一种更简单的几何结构中进行实验研究来确定所需的选择机制：具有弹性顶边界的刚性矩形Hele-Shaw通道。这种弹性-刚性通道的本构行为是非线性的，与弹性管的本构行为大体相似，但与弹性管不同的是，从未变形状态到第一近壁接触点，通道的横截面采用自相似形状。随之而来的血管几何形状的简化使得能够根据增加的初始坍塌来系统地研究重新开放的动力学。我们发现，对于低水平的初始坍塌，单个中心对称的手指在通道中传播，其形状由尖端曲率决定。随着坍塌程度的增加，沟槽横截面发展出一个接近相对壁面接触的中心区域，手指形状平滑地演变为“扁平”手指，其几何形状由沟道壁附近强烈的深度梯度决定。我们证明了平头重开的模式类似于在管子中观察到的尖指。它的传播是由船舶在高坍塌时的极端横截面轮廓支撑的，而船舶的顺应性是稳定它所必需的。一个基于耗散功率的简单标度论证表明，在较高的传播速度下，当这种重新开启模式变得有利于取代弹性通道壁而不是粘性流体时，它是首选的。
Motivated by the reopening mechanics of strongly collapsed airways, we study the steady propagation of an air finger through a collapsed oil-filled channel with a single compliant wall. In a previous study using fully compliant elastic tubes, a ‘pointed’ air finger was found to propagate at high speed and low pressure, which, if clinically accessible, offers the potential for rapid reopening of highly collapsed airways with minimal tissue damage (Heap & Juel Phys. Fluids, vol. 20 (8), 2008, 081702). The mechanism underlying the selection of that pointed finger, however, remained unexplained. In this paper, we identify the required selection mechanism by conducting an experimental study in a simpler geometry: a rigid rectangular Hele-Shaw channel with an elastic top boundary. The constitutive behaviour of this elasto-rigid channel is nonlinear and broadly similar to that of an elastic tube, but unlike the tube, the channel’s cross-section adopts self-similar shapes from the undeformed state to the point of first near wall contact. The ensuing simplification of the vessel geometry enables the systematic investigation of the reopening dynamics in terms of increasing initial collapse. We find that for low levels of initial collapse, a single centred symmetric finger propagates in the channel and its shape is set by the tip curvature. As the level of collapse increases, the channel cross-section develops a central region of near opposite wall contact, and the finger shape evolves smoothly towards a ‘flat-tipped’ finger whose geometry is set by the strong depth gradient near the channel walls. We show that the flat-tipped mode of reopening is analogous to the pointed finger observed in tubes. Its propagation is sustained by the vessel’s extreme cross-sectional profile at high collapse, while vessel compliance is necessary to stabilise it. A simple scaling argument based on the dissipated power reveals that this reopening mode is preferred at higher propagation speeds when it becomes favourable to displace the elastic channel wall rather than the viscous fluid.
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影响因子：
8.6
作者：
Pihler-Puzovic, D.;Illien, P.;Juel, A.
通讯作者：
Juel, A.
影响因子：
3.3
作者：
GAVER, DP;SAMSEL, RW;SOLWAY, J
通讯作者：
SOLWAY, J
位移在弹性膜下流动。
影响因子：
3.7
作者：
Pihler-Puzovic D
通讯作者：
Pihler-Puzovic D
管的几何形状可以迫使气泡传播行为发生类似开关的转变
影响因子：
4.6
作者：
De Lózar A
通讯作者：
De Lózar A