Research Papers

Modeling Inspiratory Flow in a Porcine Lung Airway

[+] Author and Article Information
Peshala P. T. Gamage

Biomedical Acoustics Research
Laboratory (BARL),
Department of Mechanical and
Aerospace Engineering,
College of Engineering and Computer Science,
University of Central Florida,
ENGR 1, Room 428,
12760 Pegasus Boulevard,
Orlando, FL 32816
e-mail: peshala@knights.ucf.edu

Fardin Khalili

Biomedical Acoustics Research
Laboratory (BARL),
Department of Mechanical and
Aerospace Engineering,
College of Engineering and Computer Science,
University of Central Florida,
ENGR 1, Room 428,
12760 Pegasus Boulevard,
Orlando, FL 32816
e-mail: fardin@knights.ucf.edu

M. D. Khurshidul Azad

Biomedical Acoustics Research
Laboratory (BARL),
Department of Mechanical and
Aerospace Engineering,
College of Engineering and Computer Science,
University of Central Florida,
ENGR 1, Room 428,
12760 Pegasus Boulevard,
Orlando, FL 32816
e-mail: khurshid@knights.ucf.edu

Hansen A Mansy

Biomedical Acoustics Research
Laboratory (BARL),
Department of Mechanical and
Aerospace Engineering,
College of Engineering and Computer Science,
University of Central Florida,
ENGR 1, Room 428,
12760 Pegasus Boulevard,
Orlando, FL 32816
e-mail: hansen.mansy@ucf.edu

1Corresponding author.

Manuscript received August 2, 2017; final manuscript received October 31, 2017; published online March 19, 2018. Assoc. Editor: Ching-Long Lin.

J Biomech Eng 140(6), 061003 (Mar 19, 2018) (11 pages) Paper No: BIO-17-1336; doi: 10.1115/1.4038431 History: Received August 02, 2017; Revised October 31, 2017

Inspiratory flow in a multigeneration pig lung airways was numerically studied at a steady inlet flow rate of 3.2 × 10−4 m3/s corresponding to a Reynolds number of 1150 in the trachea. The model was validated by comparing velocity distributions with previous measurements and simulations in simplified airway geometries. Simulation results provided detailed maps of the axial and secondary flow patterns at different cross sections of the airway tree. The vortex core regions in the airways were visualized using absolute helicity values and suggested the presence of secondary flow vortices where two counter-rotating vortices were observed at the main bifurcation and in many other bifurcations. Both laminar and turbulent flows were considered. Results showed that axial and secondary flows were comparable in the laminar and turbulent cases. Turbulent kinetic energy (TKE) vanished in the more distal airways, which indicates that the flow in these airways approaches laminar flow conditions. The simulation results suggested viscous pressure drop values comparable to earlier studies. The monopodial asymmetric nature of airway branching in pigs resulted in airflow patterns that are different from the less asymmetric human airways. The major daughters of the pig airways tended to have high airflow ratios, which may lead to different particle distribution and sound generation patterns. These differences need to be taken into consideration when interpreting the results of animal studies involving pigs before generalizing these results to humans.

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Fig. 1

(a) Meshed pig airway, (b) zoomed image of the mesh, and (c) zoomed image of a section with prism layer mesh

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Fig. 2

Comparison between simulated and measured velocity distributions at different bifurcation planes for an inlet Re = 1500

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Fig. 3

(a) Pressure drop comparison between simulation and experiment and (b) simplified symmetric pig airway and pressure probe locations

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Fig. 4

(a) Velocity profile in the bifurcation plane, (b) secondary velocity vectors on section 1-1', (c) section 2-2', (d) section 3-3', (e) axial velocity profiles on section 1-1', (f) section 2-2', and (g) section 3-3'

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Fig. 5

A map of the axial velocity at a cross section that includes the trachea and the main bronchi (a) with (b) without (blocked) tracheal bronchus. (c) Iso-surface of the mean velocity magnitude.

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Fig. 6

(a) Secondary velocity streamlines and axial velocity distributions at cross section of main bronchi and (b) a zoomed view of the helicity iso-surface and the secondary flow vectors near the carina

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Fig. 7

The axial velocity and secondary flow streamlines at different cross section in right lung

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Fig. 8

The axial velocity and secondary flow streamlines at different cross section in left lung

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Fig. 9

(a) Absolute helicity iso-surface of the airway tree and (b) TKE distribution at a cross section of airway tree

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Fig. 10

(a) Velocity distribution at airway sections for laminar and turbulent (k−ω) models and (b) axial velocity profiles in the trachea and mainstem bronchi

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Fig. 11

Flow ratio percentages in to different sections of the airway (refer Figs. 7 and 8 for location of the sections)

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Fig. 12

Comparison of the pressure drop per unit length (box and whiskers plot)




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