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Research Papers: Flows in Complex Systems

On Nano-Ellipsoid Transport and Deposition in the Lung First Bifurcation-Effect of Slip Correction

[+] Author and Article Information
Lin Tian

School of Aerospace, Mechanical and
Manufacturing Engineering,
RMIT University,
Bundoora, VIC 3083, Australia
e-mail: lin.tian@rmit.edu.au

Goodarz Ahmadi

Fellow ASME
Department of Mechanical and
Aeronautical Engineering,
Clarkson University,
Potsdam, NY 13676
e-mail: gahmadi@clarkson.edu

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received November 23, 2015; final manuscript received June 22, 2016; published online July 21, 2016. Assoc. Editor: Francine Battaglia.

J. Fluids Eng 138(10), 101101 (Jul 21, 2016) (14 pages) Paper No: FE-15-1858; doi: 10.1115/1.4033997 History: Received November 23, 2015; Revised June 22, 2016

Recent rapid development of industrial usage of carbon nanotubes (CNTs) has raised health concerns as these engineered elongated particles resemble the appearance of asbestos, which is a well-known inhalation hazard. While CNTs have elongated rod shaped structure similar to asbestos, they are nanosized, and therefore, their motions are strongly affected by Brownian diffusion. The available studies in this area are rather limited and details of the nanofiber dynamics along the transport route are largely unknown. In this study, the CNTs were modeled as elongated ellipsoids and their full motions including the coupled translational and rotational movement in the human tracheobronchial first airway bifurcation were analyzed. Particular attention was given to the effects of the slip-correction and Brownian motion, which are critical to the accuracy of the modeling of motions of nanoscale CNTs in free molecular and transition regimes.

Copyright © 2016 by ASME
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Figures

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Fig. 1

Asymmetric tracheobronchial bifurcation model

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Fig. 2

Computational grid: (a) schematic view inside the airway bifurcation, (b) surface mesh at the inlet, (c) mesh plane view of the bifurcation, and (d) mesh near the vicinity of the carinal ridge

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Fig. 3

Velocity and turbulence profiles along the line of a cross section near the bifurcation region for the three different mesh sizes

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Fig. 4

Schematic of an ellipsoidal fiber and the corresponding coordinate

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Fig. 5

Linear transformation of the coordinate systems: (a) Euler angles and (b) Euler's quaternion

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Fig. 6

Comparison of fiber transport characteristics in the trachea and the first bifurcation for a 1 μm diameter fiber with aspect ratio = 4 (length = 4 μm), breathing rate = 37 L/min: (a) laminar flow, (b) turbulent flow, (c) turbulent flow with Brownian excitation, and (d) laminar flow with Brownian excitation

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Fig. 7

Comparison of fiber transport characteristics in the trachea and the first bifurcation for a 1 μm diameter fiber with aspect ratio = 12 (length = 12 μm), breathing rate = 37 L/min: (a) laminar flow, (b) turbulent flow, (c) turbulent flow with Brownian excitation, and (d) laminar flow with Brownian excitation

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Fig. 8

Comparison of fiber transport characteristics in the trachea and the first bifurcation for a 10 μm diameter fiber with aspect ratio = 4 (length = 40 μm), breathing rate = 37 L/min: (a) laminar flow, (b) turbulent flow, (c) turbulent flow with Brownian excitation, and (d) laminar flow with Brownian excitation

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Fig. 9

Comparison of fiber transport characteristics in the trachea and the first bifurcation for a 10 μm diameter fiber with aspect ratio = 12 (length = 120 μm), breathing rate = 37 L/min: (a) laminar flow, (b) turbulent flow, (c) turbulent flow with Brownian excitation, and (d) laminar flow with Brownian excitation

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Fig. 10

Comparison of fiber transport characteristics in the trachea and the first bifurcation for a 0.01 μm diameter fiber with aspect ratio = 4 (length = 0.04 μm), flow rate = 37 L/min: (a) laminar flow modeling, (b) turbulent flow modeling, (c) turbulent flow modeling with Brownian excitation, and (d) laminar flow modeling with Brownian excitation

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Fig. 11

Comparison of fiber transport characteristics in the trachea and the first bifurcation for a 0.01 μm diameter fiber with aspect ratio = 12 (length = 0.12 μm), flow rate = 37 L/min: (a) laminar flow modeling, (b) turbulent flow modeling, (c) turbulent flow modeling with Brownian excitation, and (d) laminar flow modeling with Brownian excitation

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Fig. 12

Comparison of the fiber deposition efficiency as predicted by the combined turbulent flow and Brownian model with earlier experimental data

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Fig. 13

Comparison of the fiber deposition efficiency as predicted by different numerical models

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Fig. 15

The fiber deposition efficiency—comparison of translational versus rotational Cunningham corrections

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Fig. 16

Comparison of the fiber deposition efficiency with and without the Brownian rotational motions

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Fig. 14

Comparison of the fiber deposition efficiency—effect of the slip-correction factors

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