Computational fluid dynamics (CFD) simulations were performed using large-scale models of the human lung airway and unsteady periodic breathing conditions. The computational domain included fully coupled representations of the orotracheal region and large conducting zone up to generation four (G4) obtained from patient-specific CT data, and the small conducting zone (to the 16th generation) obtained from a stochastically generated airway tree with statistically realistic morphological characteristics. A reduced-geometry airway model was used, in which several airway branches in each generation were truncated, and only select flow paths were retained to the 16th generation. The inlet and outlet flow boundaries corresponded to the oral opening, the physical inlet/outlet boundaries at the terminal bronchioles, and the unresolved airway boundaries created from the truncation procedure. The total flow rate was specified according to the expected ventilation pattern for a healthy adult male, which was supplied by the whole-body modeling software HumMod. The unsteady mass flow distribution at the distal boundaries was prescribed based on a preliminary steady-state simulation with an applied flow rate equal to the average flow rate during the inhalation phase of the breathing cycle. In contrast to existing studies, this approach allows fully coupled simulation of the entire conducting zone, with no need to specify distal mass flow or pressure boundary conditions a priori, and without the use of impedance or one-dimensional (1D) flow models downstream of the truncated boundaries. The results show that: (1) physiologically realistic flow is obtained in the model, in terms of cyclic mass conservation and approximately uniform pressure distribution in the distal airways; (2) the predicted alveolar pressure is in good agreement with correlated experimental data; and (3) the use of reduced-order geometry modeling allows accurate and efficient simulation of large-scale breathing lung flow, provided care is taken to use a physiologically realistic geometry and to properly address the unsteady boundary conditions.
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October 2014
Research-Article
Cyclic Breathing Simulations in Large-Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles
D. Keith Walters,
D. Keith Walters
Department of Mechanical Engineering,
Mississippi State University
,Starkville, MS 39762
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Greg W. Burgreen,
Greg W. Burgreen
CAVS SimCenter,
Mississippi State University
,Starkville, MS 39762
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Robert L. Hester,
Robert L. Hester
Department of Physiology,
University of Mississippi Medical Center
,Jackson, MS 39216
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David S. Thompson,
David S. Thompson
Department of Aerospace Engineering,
Mississippi State University
,Starkville, MS 39762
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David M. Lavallee,
David M. Lavallee
Department of Aerospace Engineering,
Mississippi State University
,Starkville, MS 39762
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William A. Pruett,
William A. Pruett
Department of Physiology,
University of Mississippi Medical Center
,Jackson, MS 39216
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Xiao Wang
Xiao Wang
CAVS SimCenter,
Mississippi State University
,Starkville, MS 39762
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D. Keith Walters
Department of Mechanical Engineering,
Mississippi State University
,Starkville, MS 39762
Greg W. Burgreen
CAVS SimCenter,
Mississippi State University
,Starkville, MS 39762
Robert L. Hester
Department of Physiology,
University of Mississippi Medical Center
,Jackson, MS 39216
David S. Thompson
Department of Aerospace Engineering,
Mississippi State University
,Starkville, MS 39762
David M. Lavallee
Department of Aerospace Engineering,
Mississippi State University
,Starkville, MS 39762
William A. Pruett
Department of Physiology,
University of Mississippi Medical Center
,Jackson, MS 39216
Xiao Wang
CAVS SimCenter,
Mississippi State University
,Starkville, MS 39762
Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received January 29, 2013; final manuscript received April 21, 2014; published online July 24, 2014. Assoc. Editor: Francine Battaglia.
J. Fluids Eng. Oct 2014, 136(10): 101101 (10 pages)
Published Online: July 24, 2014
Article history
Received:
January 29, 2013
Revision Received:
April 21, 2014
Citation
Keith Walters, D., Burgreen, G. W., Hester, R. L., Thompson, D. S., Lavallee, D. M., Pruett, W. A., and Wang, X. (July 24, 2014). "Cyclic Breathing Simulations in Large-Scale Models of the Lung Airway From the Oronasal Opening to the Terminal Bronchioles." ASME. J. Fluids Eng. October 2014; 136(10): 101101. https://doi.org/10.1115/1.4027485
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