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

Axial and secondary velocity profiles were measured in a model human centra l airway to clarify the oscillatory flow structure during high-frequency os cillation We used a rigid model of human airways consisting of asymmetrical bifurcations up to third generation. Velocities in each branch of the bifu rcations were measured by two-color laser-Doppler velocimeter. The secondar y velocity magnitudes and the deflection of axial velocity were dependent n ot only on the branching angle and curvature ratio of each bifurcation, but also strongly depended on the shape of the path generated by the cascade o f branches. Secondary flow velocities were higher in the left bronchus than in the right bronchus. This spatial variation of secondary flow was well c orrelated with differing gas transport rates between the left and right mai n bronchus.