Abstract：
Unsteady respiratory airflow characteristics play a crucial role in understanding the deposition of toxic particles and inhaled aerosol drugs in the human respiratory tract. Considering the variations in respiratory flow rate and glottis motion under different respiratory frequencies, these respiratory airflow characteristics are studied by large-eddy simulations, including pressure field, power loss, modal spatial patterns, and vortex structures. Firstly, the results reveal that varying respiratory frequencies significantly affect airflow unsteadiness, turbulent evolution, and vortex structure dissipation, as they increase the complexity and butterfly effect introduced by the turbulent disturbance. Secondly, the pressure drops and flow rate at the glottis also conform to a power-law relationship considering the respiratory physiological characteristics, especially under low respiratory frequencies. Glottis motion plays different roles in energy consumption during inspiration and expiration, and its magnitude can be predicted using a polynomial function based on glottis area and respiratory flowrate under different respiratory frequencies. Finally, modal decomposition can be effectively applied to the study of respiratory flow characteristics, but we recommend separately studying the inspiration and expiration. The spatial distribution of the dominant mode characterizes the majority of respiratory flow characteristics and are influenced by respiratory frequency. Spectral entropy results indicate that glottis motion and slow breathing both delay the transitions in the upper respiratory tract during inspiration and expiration. These results confirm that the respiratory physiology characteristics under different respiratory frequencies have a significant impact on the unsteady respiratory airflow characteristics and warrant further study.
摘要：
不稳定的呼吸气流特征在理解有毒颗粒和吸入的气溶胶药物在人体呼吸道中的沉积中起着至关重要的作用。考虑到不同呼吸频率下呼吸流速和声门运动的变化，这些呼吸气流特性是通过大涡模拟研究的，包括压力场，功率损耗,模态空间模式，和涡旋结构。首先,结果表明，不同的呼吸频率显著影响气流不稳定，湍流演化,和涡流结构耗散，因为它们增加了湍流扰动引入的复杂性和蝴蝶效应。其次,考虑到呼吸的生理特性，声门处的压力下降和流速也符合幂律关系，尤其是在低呼吸频率下。声门运动在吸气和呼气期间的能量消耗中起着不同的作用，根据不同呼吸频率下的声门面积和呼吸流速，可以使用多项式函数预测其大小。最后,模态分解可以有效地应用于呼吸流量特性的研究,但我们建议分别研究吸气和呼气。主导模式的空间分布表征了大多数呼吸流量特性，并受呼吸频率的影响。频谱熵结果表明，在吸气和呼气期间，声门运动和缓慢呼吸都会延迟上呼吸道的过渡。这些结果证实了不同呼吸频率下的呼吸生理特性对非稳态呼吸气流特性具有显著影响,值得进一步研究。
