Enhancement of gas transfer due to the convective resonance in the bifurcating tube of the airway

气体在气道中由于振荡流而交换，并且气体交换机制受到各种因素的影响，诸如气道的形态、气道的开放、气道内表面分泌的表面活性剂等。在天然肺中，气体交换过程是非常有效的，并且对需氧量高度敏感，因此有必要阐明气道中的气体交换过程。在气道中，气体通过多分支网络中的振荡流进行传输，在分叉管弯曲部分诱导的二次流导致气体传输过程的增强，这一过程被称为“对流共振”。因此，我们关注了对流共振现象，本研究的目的是阐明对流共振引起天然肺中气体传输增强的流体力学特征。对流共振对高频振荡技术可能是有效的，利用对流共振的作用可以使人工通气更有效。在这项研究中，我们进行了实验和数值研究，以确认由于在弯曲部分的二次流对流共振的有效性。同时考虑了气道扩张性的影响，建立了真实的气道模型。气道的可扩张性将限制湍流的产生，从而影响气道内气体传递的增强。

The gas is exchanged in the airway due to the oscillatory flow and the gas exchange mechanisms are affected by various factors such as morphology of airway, opening of airway, surfactant secreted on the inner surface of airway and others. In the natural lung, the gas exchange process is remarkably efficient and is highly sensitive to the oxygen demand, thus it is necessary to clarify the gas exchange process in the airway. In the airway, the gas is transported by the ocillatory flow in the multi-branching network and the secondary flow induced in the curved portion of bifurcating tube causes to enhance the gas transfer process, and this process is called "convective resonance". So we payed attention to the phenomena of convective resonance and the purpose of this study it to clarify the fluid mechanical feature of convective resonance causing to enhance the gas transfer in the natural lung. The convective resonance may be effective to the high frequency oscillation technology and artificial ventilation will become more effective by utilizing the effect of convetive resonance. In this study we performed both experiments and numerical studies to confirm the effectiveness of convective resonance due to the secondary flow in the curved portions. We also took into acount the effect of distensibility of the airway and constructed the realistic airway model. The distensibility of the airway will restrict the generation of turbulence, which affects the enhancement of gas transfer in the airway.