循环呼吸模式对人体气管支气管内气流运动影响的仿真分析

Numerical analysis of the effect of the cyclic respiratory mode on the airflow movement in human tracheobronchial airways

目的:研究人体气管支气管内的气流运动特性,了解有毒气溶胶或药物治疗气溶胶在人体气管支气管内不同部位的沉积模式。方法:应用计算流体动力学方法对人体在循环呼吸模式下气管支气管内的气流运动特性进行数值模拟,分析循环呼吸模式对气管支气管内的气流组织形式以及气流运动对呼吸道壁面的影响。结果:在吸气加速阶段,气管支气管平面内逐渐形成抛物线型的速度分布,气管支气管内各个截面上逐渐形成二次涡流运动,内壁形成高剪应力区。在呼气阶段,支气管内的二次气流运动经历了从2个涡流到4个涡流的运动变化过程。气流经过多级分支的效果是使速度的分布均匀化,特别使在同级两个支气管轴线共处的平面内的速度分布,在经过几级汇合后,轴线处的速度峰值分布现象会消失而变得均匀。结论:循环呼吸模式下壁面受到的剪应力周期性改变方向,引起壁面劳损和组织损伤的可能性增大,同时在这些部位容易造成气溶胶的沉积。

Objective：To analyze the deposition patterns for the toxic aerosols or the pharmaceutical aerosols in human tracheobronchial airways based on the characteristics of the human tracheobronchial airflow movement. Methods： The airflow movement characteristics in human tracheobronchial airways were investigated using the method of computational fluid dynamics（CFD）. The airflow patterns in human tracheobronchial airways and the effect of airflow movement on the wall of the tracheobronchial airways were analysed. Results： During the inhalation phase, the parabolic shape velocity profiles appeared in the middle plane of the bifurcation. Secondary vortices were generated in the cross sections of the model, which led to the generation of the high shearing strength zone near the inner wall of the model. During the exhalation phase, the secondary flows in the bifurcation experienced the change from two vortices to four vortices. The airflow flowing through the bifurcations led to the uniform distribution of the velocity, which especially made the maximum velocity around the axis disappear and the velocity profiles become uniform in the middle plane of the bifurcation. Conclusion：The direction of the shearing strength acting on the wall varied periodically, not only resulting in the increase in the probability of the wall strain and tissue injury, but also in easy aerosol deposition in these areas.