To provide a quantitative description of the convection field of gas transport through the lung under both low and high-frequency ventilation conditions, volume-cycled, purely oscillatory flow has been investigated in a symmetrically bifurcating model bronchial bifurcation. Significant differences in the flow properties that developed as the Reynolds number varied from 750 to 950 and the dimensionless frequency varied from 3 to 12 are described. At low frequency, the axial velocity field was found to approximate closely that of a steady flow through a bifurcation. However, even at α = 3, secondary velocity fields were confined to within a few diameters of the bifurcation, with less than 10 percent of the magnitude of the axial velocity. At high frequency they were still slower and more limited. These secondary velocity observations are discussed in terms of a physical mechanism balancing inviscid centripetal acceleration with viscous retardation. As the dimensionless frequency increased but the flow amplitude decreased, the magnitude of the axial drift velocity field was found to decrease. In addition, a burst of high-frequency velocity fluctuations was detected in both the axial and secondary velocity measurements in the parent tube, in low-frequency flow, during the deceleration phase of expiration. The position and timing of this burst suggest that it derives from the free shear layer in the parent tube. Stability criteria for the flow were therefore evaluated.

1.
Pedley
T. J.
, “
Pulmonary fluid dynamics
,”
Ann. Rev. Fluid Mech.
,
9
,
229
274
,
1977
.
2.
Pedley, T. J., and Kamm, R. D., “Dynamics of gas flow and pressure-flow relationships,” in: The Lung: Scientific Foundations, R. G. Crystal, J. B. West, et al., eds., Raven Press, Ltd., New York, 1991.
3.
Grotberg
J. B.
, “
Pulmonary flow and transport phenomena
,”
Ann. Rev. Fluid Mech.
,
9
,
229
274
,
1994
.
4.
Pacome, J.-J., “Structures d’ecoulement et pertes de charges calculees dans le modele d’arbre bronchique de Weibel,” Ph.D. thesis, Paul Sabatier University, 1975.
5.
Schroter
R. C.
, and
Sudlow
M. F.
, “
Flow patterns in models of the human bronchial airways
,”
Respir. Physiol.
,
7
,
341
355
,
1969
.
6.
Olson, D. E., “Fluid mechanics relevant to respiration: flow within curved or elliptical tubes and bifurcating systems,” Ph.D. thesis, Imperial Coll. London, 1971.
7.
Collins
J. M.
,
Shapiro
A. H.
,
Kimmel
E.
, and
Kamm
R. D.
, “
The steady expiratory pressure-flow relation in a model pulmonary bifurcation
,”
ASME JOURNAL OF BIOMECHANICAL ENGINEERING
,
115
,
299
305
,
1993
.
8.
Menon
A. S.
,
Weber
M. E.
, and
Chang
H. K.
, “
Model study of flow dynamics in human central airways. Part III: oscillatory velocity profiles
,”
Respir. Physiol.
,
55
,
255
275
,
1984
.
9.
Jan
D. L.
,
Shapiro
A. H.
, and
Kamm
R. D.
, “
Some features of oscillatory flow in a model bifurcation
,”
J. Appl. Physiol.
,
67
,
147
159
,
1989
.
10.
Gatlin, B., Cuicchi, C. E., Hammersley, J. R., Olson, D. E., Reddy, R. N., and Burnside, G. G., “Computational Simulation of Steady and Oscillating Flow in Branching Tubes,” Proc. Biomed. Fluids Eng. Symp., ASME FED-Vol. 212, 1–8, 1995.
11.
Haselton
F. R.
, and
Scherer
P. W.
, “
Flow visualization of steady streaming in oscillatory flow through a bifurcating tube
,”
J. Fluid Mech.
,
123
,
315
333
,
1982
.
12.
Scherer
P. W.
, and
Haselton
F. R.
, “
Convective exchange in oscillatory flow through bronchial-tree models
,”
J. Appl. Physiol.: Respirat. Environ. Excercise Physiol.
,
53
,
1023
1033
,
1982
.
13.
Grotberg
J. B.
, “
Volume-cycled oscillatory flow in a tapered channel
,”
J. Fluid Mech.
,
141
,
249
264
,
1984
.
14.
Gaver
D. P.
, and
Grotberg
J. B.
, “
An experimental investigation of oscillating flow in a tapered channel
,”
J. Fluid Mech.
,
172
,
47
61
,
1986
.
15.
Budwig, R. S., “Two unsteady heat transfer experiments: I. In grid-generated isotropic turbulence; II. In laminar oscillatory flow in straight and conical tubes,” Ph.D. thesis Johns Hopkins University, 1985.
16.
Gerrard
J. H.
, and
Hughes
M. D.
, “
The flow due to an oscillating piston in a cylindrical tube: a comparison between experiment and a simple entrance flow theory
,”
J. Fluid Mech.
,
50
,
97
106
,
1971
.
17.
Popwell, R. E., and Peattie, R. A., “Transition to Turbulence in Oscillating Flows Through a Model Bronchial Bifurcation,” Advances in Bioengineering, ASME BED-Vol. 26:215–218, 1993.
18.
Budwig
R. S.
, and
Peattie
R. A.
, “
Two new circuits for hydrogen bubble flow visualization
,”
J. Phys. E: Sci. Instrum.
,
22
,
250
254
,
1989
.
19.
Batchelor, G. K., An Introduction to Fluid Mechanics, Cambridge University Press New York, 1967.
20.
Eckmann
D. M.
, and
Grotberg
J. B.
, “
Experiments on transition to turbulence in oscillatory pipe flow
,”
J. Fluid Mech.
,
222
,
329
350
,
1991
.
21.
Eckmann
D. E.
, and
Grotberg
J. B.
, “
Oscillatory flow and mass transport in a curved tube
,”
J. Fluid Mech.
,
188
,
509
527
,
1988
.
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