Measurement of axial effective diffusivity in oscillatory pipe flow by Laplace transform method

Hideki Fujioka*, Tomohiko Murakami, Kazuo Tanishita

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Analysis of gas transport in oscillatory flow though an airway model with complex geometry such as a single bifurcation, relies on the theoretical understanding of gas exchange during High-frequency oscillation; HFO. Our purpose was to develop a method for measuring the mean effective diffusivity in an oscillatory flow between two points, by applying Laplace Transform Method. The measurement time Tmax, which is the area of the Laplace integration, and the Laplace parameter s are related to the accuracy of the measured effective diffusivity, Deff. In this study, numerical analysis was carried out to investigate the Laplace Transform Method. We defined the parameter K required to obtain optimum s, and found that K ≅ 0.1. Then we applied this method to evaluate Deff in a straight tube and a single symmetrical bifurcation. The theoretical results for a straight tube agreed with the measured Deff. Deff for the bifurcating tube was greater than that for the straight tube by a factor of Dn24, that proved the effect of the secondary flow.

Original languageEnglish
Pages (from-to)3860-3866
Number of pages7
JournalNippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B
Issue number603
Publication statusPublished - 1996 Nov

ASJC Scopus subject areas

  • Mechanical Engineering


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