Experimental Investigation of Oscillatory Flow Through a Symmetrically Bifurcating Tube

[+] Author and Article Information
R. A. Peattie

Department of Engineering, Trinity College, Hartford, CT 06106

W. Schwarz

Department of Chemical Engineering, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218

J Biomech Eng 120(5), 584-593 (Oct 01, 1998) (10 pages) doi:10.1115/1.2834748 History: Received January 03, 1997; Revised February 07, 1998; Online January 23, 2008


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.

Copyright © 1998 by The American Society of Mechanical Engineers
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