Journal of Applied Physiology, Vol 49, Issue 3 417-423, Copyright © 1980 by American Physiological Society
Steady flow in a model of human central airways
A. S. Slutsky, G. G. Berdine and J. M. Drazen
We studied the pressure-flow relationships and flow distribution under
steady conditions in a model of human central airways, over a range of
tracheal Reynolds' numbers (350-30,000) by using air or helium. We found
that the Moody diagram [log coefficient of friction CF = delta P/[1/2 rho
(V2/A2)] vs. log Reynolds' number (Re)] had a slope of -1 for Re less than
500, a slope 0 for Re greater than 10,000, and slopes between -1 and 0 for
500 less than or equal to Re less than or equal to 10,000. The distribution
of flow among branches was dependent on tracheal Reynolds' number so that,
as tracheal Reynolds' number increased, the upper lobes received
proportionally less of the total flow than the lower lobes. Because the
airways in the upper lobes generally had greater branching angles than
those in the lower lobes, this result was consistent with the hypothesis
that the effective resistances introduced by branching angles was flow
dependent, increasing proportionally more the greater the angle.
