Axial gas transport due to the interaction between radial mixing and radially nonuniform axial velocities is responsible for gas transport in thick airways during High-frequency oscillatory ventilation (HFO). Because the airways can be characterized by a bifurcating tube network, the secondary flow in the curved portion of a bifurcating tube contributes to cross-stream mixing. In this study the oscillatory flow and concentration fields through a single symmetrical airway bifurcating tube model were numerically analyzed by solving three-dimensional Navier-Stokes and mass concentration equations with the SIMPLER algorithm. The simulation conditions were for a Womersley number, and Reynolds numbers in the parent tube between 200 and 1000, corresponding to in the curved portion between 2 and 80, where Dn is Dean number. For comparison with the results from the bifurcating tube, we calculated the velocity and concentration fields for fully developed oscillatory flow through a curved tube with a curvature rate of 1/10, which is identical to the curved portion of the bifurcating tube. For in the curved portion of the bifurcating tube, the flow divider and area changes dominate the axial gas transport, because the effective diffusivity is greater than in either a straight or curved tube, in spite of low secondary velocities. However, for the gas transport characteristics in a bifurcation are similar to a curved tube because of the significant effect of secondary flow.
Oscillatory Flow and Gas Transport Through a Symmetrical Bifurcation
Contributed by the Bioengineering Division for publication in the JOURNAL OF BIOMECHANICAL ENGINEERING. Manuscript received by the Bioengineering Division April 1998; revised manuscript received November 2000. Associate Editor: J. B. Grotberg.
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Fujioka, H., Oka , K., and Tanishita, K. (November 1, 2000). "Oscillatory Flow and Gas Transport Through a Symmetrical Bifurcation ." ASME. J Biomech Eng. April 2001; 123(2): 145–153. https://doi.org/10.1115/1.1352735
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