Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, IA 52242, USA.
Ann Biomed Eng. 2010 May;38(5):1836-53. doi: 10.1007/s10439-010-9956-y. Epub 2010 Feb 17.
The airflow characteristics in a computed tomography (CT) based human airway bifurcation model with rigid and compliant walls are investigated numerically. An in-house three-dimensional (3D) fluid-structure interaction (FSI) method is applied to simulate the flow at different Reynolds numbers and airway wall stiffness. As the Reynolds number increases, the airway wall deformation increases and the secondary flow becomes more prominent. It is found that the peak wall shear stress on the rigid airway wall can be five times stronger than that on the compliant airway wall. When adding tethering forces to the model, we find that these forces, which produce larger airway deformation than without tethering, lead to more skewed velocity profiles in the lower branches and further reduced wall shear stresses via a larger airway lumen. This implies that pathologic changes in the lung such as fibrosis or remodeling of the airway wall-both of which can serve to restrain airway wall motion-have the potential to increase wall shear stress and thus can form a positive feed-back loop for the development of altered flow profiles and airway remodeling. These observations are particularly interesting as we try to understand flow and structural changes seen in, for instance, asthma, emphysema, cystic fibrosis, and interstitial lung disease.
对具有刚性和弹性壁的基于计算机断层扫描 (CT) 的人体气道分叉模型中的气流特性进行了数值研究。应用内部的三维 (3D) 流固耦合 (FSI) 方法来模拟不同雷诺数和气道壁刚度下的流动。随着雷诺数的增加，气道壁变形增加，二次流变得更加明显。结果发现，刚性气道壁上的壁面剪切应力峰值可以比弹性气道壁上的强五倍。当向模型中添加系绳力时，我们发现这些力会导致气道变形大于没有系绳的情况，从而导致较低分支中的速度分布更加偏斜，并通过更大的气道内腔进一步降低壁面剪切应力。这意味着肺部的病理变化，如纤维化或气道壁重塑——这两者都可以限制气道壁运动——有可能增加壁面剪切应力，从而为改变的流动模式和气道重塑的发展形成正反馈循环。这些观察结果特别有趣，因为我们试图了解例如哮喘、肺气肿、囊性纤维化和间质性肺疾病中所见的流动和结构变化。
