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

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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.