Journal of Applied Physiology, Vol 52, Issue 6 1476-1486, Copyright © 1982 by American Physiological Society
Effects of gravity and branching on longitudinal gas mixing in glass tube models
H. Shibata, T. Okubo, T. Fuyuki, T. Takishima and N. Imaishi
We investigated the effects of gravity and branching on gas mixing in glass
tube models. The mixed gas (5% He and 5% SF6) was made to flow through a
straight tube and tubes with bifurcated branches, and the effective axial
diffusion coefficient (Deff) was measured. The direction of the branches
was varied from upward to downward by 90% turns, and the flow distribution
to each branch was separately controlled. In the case of a straight
horiontal tube, the flow velocity dependency of the Deff of He and SF6 was
observed as we expected from Aris' equation. In the case of glass tubes
with branches, the Deff of SF6 was greater in the downward-directed
branches than it was in the upward-directed branches when gas mixing
occurred at the front of the gas mixture; however, when gas mixing occurred
at the tail, the opposite effects were observed. These characteristics were
more marked at slower flow rates and when the flow to each branch was
different. Our findings suggest that gravity has an effect on gas mixing in
glass tube airway models, especially at a low flow rate and uneven flow
distribution.
