Augmentation of Axial Dispersion by Intermittent Oscillatory Flow

[+] Author and Article Information
G. Tanaka, Y. Ueda, K. Tanishita

Institute of Biomedical Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223, Japan

J Biomech Eng 120(3), 405-415 (Jun 01, 1998) (11 pages) doi:10.1115/1.2798008 History: Received November 13, 1995; Revised January 09, 1998; Online October 30, 2007


The efficiency of axial gas dispersion during ventilation with high-frequency oscillation (HFO) is improved by manipulating the oscillatory flow waveform such that intermittent oscillatory flow occurs. We therefore measured the velocity profiles and effective axial gas diffusivity during intermittent oscillatory flow in a straight tube to verify the intermittency augmentation effect on axial gas transfer. The effective diffusivity was dependent on the flow patterns and significantly increased with an increase in the duration of the stationary phase. It was also found that the ratio of effective diffusivity to molecular diffusivity is two times greater than that in sinusoidal oscillatory flow. Moreover, turbulence during deceleration or at the beginning of the stationary phase further augments axial dispersion, with the effective diffusivity being over three times as large, thereby proving that the use of intermittent oscillatory flow effectively augments axial dispersion for ventilation with HFO.

Copyright © 1998 by The American Society of Mechanical Engineers
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