Journal article
Numerical study of high frequency oscillatory air flow and convective mixing in a CT-based human airway model
Annals of biomedical engineering, Vol.38(12), pp.3550-3571
12/2010
DOI: 10.1007/s10439-010-0110-7
PMCID: PMC3064990
PMID: 20614248
Abstract
High frequency oscillatory ventilation (HFOV) is considered an efficient and safe respiratory technique to ventilate neonates and patients with acute respiratory distress syndrome. HFOV has very different characteristics from normal breathing physiology, with a much smaller tidal volume and a higher breathing frequency. In this work, the high frequency oscillatory flow is studied using a computational fluid dynamics (CFD) analysis in three different geometrical models with increasing complexity: a straight tube, a single-bifurcation tube model, and a computed-tomography (CT)-based human airway model of up to seven generations. We aim to understand the counter-flow phenomenon at flow reversal and its role in convective mixing in these models using sinusoidal waveforms of different frequencies and Reynolds numbers. Mixing is quantified by the stretch rate analysis. In the straight-tube model, coaxial counter flow with opposing fluid streams is formed around flow reversal, agreeing with an analytical Womersley solution. However, counter flow yields no net convective mixing at end cycle. In the single-bifurcation model, counter flow at high Re is intervened with secondary vortices in the parent (child) branch at end expiration (inspiration), resulting in an irreversible mixing process. For the CT-based airway model three cases are considered, consisting of the normal breathing case, the high-frequency-normal-Re case, and the HFOV case. The counter-flow structure is more evident in the high-frequency-normal-Re case than the HFOV case. The instantaneous and time-averaged stretch rates at the end of two breathing cycles and in the vicinity of flow reversal are computed. It is found that counter flow contributes about 20% to mixing in HFOV.
Details
- Title: Subtitle
- Numerical study of high frequency oscillatory air flow and convective mixing in a CT-based human airway model
- Creators
- Jiwoong Choi - Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, Iowa 52242Guohua Xia - Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, Iowa 52242Merryn H Tawhai - Bioengineering Institute, The University of Auckland, Auckland, New ZealandEric A Hoffman - Department of Biomedical Engineering, The University of Iowa, Iowa City, Iowa 52242Ching-Long Lin - Department of Mechanical and Industrial Engineering, The University of Iowa, Iowa City, Iowa 52242
- Resource Type
- Journal article
- Publication Details
- Annals of biomedical engineering, Vol.38(12), pp.3550-3571
- DOI
- 10.1007/s10439-010-0110-7
- PMID
- 20614248
- PMCID
- PMC3064990
- ISSN
- 0090-6964
- eISSN
- 1573-9686
- Language
- English
- Date published
- 12/2010
- Academic Unit
- Roy J. Carver Department of Biomedical Engineering; Radiology; Mechanical Engineering; Internal Medicine
- Record Identifier
- 9984051996702771
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