Spatial and temporal variation of secondary flow during intermittent oscillatory flow in model human central airways

摘要

Gas transport in the central airways during high-frequency oscillation (HFO) is governed by Taylor-type dispersion with oscillatory flow, being called augmented dispersion [1]. Augmented dispersion occurs due to an interaction between a non-uniform axial velocity profile and effective lateral mixing which promotes axial dispersion at higher frequencies. Therefore, to improve axial dispersion in HFO flow, lateral mixing effects such as molecular diffusion, secondary flow, or turbulence must be introduced. We previously proposed a new method to introduce lateral mixing by intermittent oscillatory flow [2]; namely, axial dispersion was enhanced by introducing a stationary period following maximum displacement, which provides the necessary time for generating a uniform concentration profile. We also found out that the efficiency of augmented dispersion in the multiple bifurcating tubes is improved by intermittent oscillatory flow. Thus we need to know the intermittent oscillatory flow structure in detail in order to interpret the augmented axial gas transport. The purpose of this study is to clarify the intermittent oscillatory flow structure in the multiple bifurcating tubes by the measurement of LDV.