Oscillatory flow and gas transport through a symmetrical bifurcation

H. Fujioka, K. Oka, K. Tanishita

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)


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, α=9.1 and Reynolds numbers in the parent tube between 200 and 1000, corresponding to Dn24 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 Dn24≤10 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 Dn24≥20, the gas transport characteristics in a bifurcation are similar to a curved tube because of the significant effect of secondary flow.

Original languageEnglish
Pages (from-to)145-153
Number of pages9
JournalJournal of Biomechanical Engineering
Issue number2
Publication statusPublished - 2001 May 9
Externally publishedYes

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physiology (medical)


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