Journal of Applied Physiology, Vol 57, Issue 3 665-673, Copyright © 1984 by American Physiological Society
Pressure excursions during oscillatory flow in a branching network of tubes
R. Akhavan and R. D. Kamm
The pressure difference across individual branches of a four-generation
network of branching tubes was measured with the objective of obtaining
general laws to describe the pressure drop in the airways under conditions
of oscillatory flow. Fourier decomposition showed that the pressure signals
consisted of a dominant component at the excitation frequency
("fundamental") and a "first harmonic" of smaller magnitude. For values of
the ratio Re/alpha less than 200, the fundamental mainly represented fluid
acceleration, whereas the first harmonic reflected the effects both of
viscous dissipation and the change in total cross-sectional area between
parent and daughter generations. For values of Re/alpha greater than 200,
the magnitude of the fundamental was considerably larger than that due to
fluid acceleration alone, suggesting the possibility of onset of turbulence
in the branching network. These pressure measurements were applied to a
simple model of the dog lung to predict total airway resistance. The
results are found to be in substantial agreement with physiological
measurements.
