Lin Ching-Long, Tawhai Merryn H, McLennan Geoffrey, Hoffman Eric A
Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, IA 52242, USA.
Respir Physiol Neurobiol. 2007 Aug 1;157(2-3):295-309. doi: 10.1016/j.resp.2007.02.006. Epub 2007 Feb 14.
A computational fluid dynamics technique is applied to understand the relative importance of the upper and intra-thoracic airways and their role in determining central airflow patterns with particular attention paid to the importance of turbulence. The geometry of the human upper respiratory tract is derived from volumetric scans of a volunteer imaged via multidetector-row computed tomography. Geometry 1 consists of a mouthpiece, the mouth, the oropharynx, the larynx, and the intra-thoracic airways of up to six generations. Geometry 2 comprises only the intra-thoracic airways. The results show that a curved sheet-like turbulent laryngeal jet is observed only in geometry 1 with turbulence intensity in the trachea varying from 10% to 20%, whereas the turbulence in geometry 2 is negligible. The presence of turbulence is found to increase the maximum localised wall shear stress by three-folds. The proper orthogonal decomposition analysis reveals that the regions of high turbulence intensity are associated with Taylor-Görtler-like vortices. We conclude that turbulence induced by the laryngeal jet could significantly affect airway flow patterns as well as tracheal wall shear stress. Thus, airflow modeling, particularly subject specific evaluations, should consider upper as well as intra-thoracic airway geometry.
应用计算流体动力学技术来了解上呼吸道和胸内气道的相对重要性，以及它们在确定中心气流模式中的作用，并特别关注湍流的重要性。人类上呼吸道的几何结构源自通过多排探测器计算机断层扫描对一名志愿者进行容积扫描所得。几何结构1包括一个接口管、口腔、口咽、喉部以及多达六代的胸内气道。几何结构2仅包括胸内气道。结果表明，仅在几何结构1中观察到弯曲的片状湍流喉射流，气管中的湍流强度在10%至20%之间变化，而几何结构2中的湍流可忽略不计。发现湍流的存在使最大局部壁面剪应力增加了三倍。本征正交分解分析表明，高湍流强度区域与类泰勒-戈特勒涡旋有关。我们得出结论，喉射流引起的湍流会显著影响气道流动模式以及气管壁剪应力。因此，气流建模，尤其是针对特定个体的评估，应考虑上呼吸道以及胸内气道的几何结构。
