RT Journal Article ID 5abad1863cfe43f0 A1 Sakai, Eiji A1 Watanabe, Toshinori A1 Himeno, Takehiro T1 GENERATION MECHANISM OF UNIDIRECTIONAL FLOW JF Journal of Flow Visualization and Image Processing JO JFV YR 2006 FD 2006-09-25 VO 13 IS 2 SP 113 OP 132 AB It is widely known that a unidirectional flow is generated in the avian lung during a breathing process. Though the unidirectional flow should be caused by a kind of an aerodynamic valve, its generation mechanism is not fully understood. In the present study, therefore, the oscillatory flow field in a right-angle branched tube, that was a bifurcation model of the avian trachea, was visualized and analyzed both experimentally and numerically to reveal the mechanisms of the unidirectional flow. The experimental results showed that a separation vortex observed at the entrance of a side-daughter tube played an important role for generation of the unidirectional net flow. The convective inertia was also suggested to be important in the process. From the numerical simulation, the details of the flow mechanism were revealed. The inertia force was found to drive the unidirectional flow during the whole period of oscillation. A good correlation was found between the pressure drop in the branched tube due to the separation vortex and the induced velocity of the unidirectional flow. PB Begell House LK https://www.dl.begellhouse.com/journals/52b74bd3689ab10b,1f0a4b485b1bc01f,5abad1863cfe43f0.html