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Fundamental Issues and Canonical Flows

Time-Dependent Deposition of Micro- and Nanofibers in Straight Model Airways

[+] Author and Article Information
Sofie M. Högberg, Hans O. Åkerstedt, Elise Holmstedt

Fluid Mechanics,  Luleå University of Technology, SE-97187, Luleå, Sweden

T. Staffan Lundström1

Fluid Mechanics,  Luleå University of Technology, SE-97187, Luleå, Swedenstaffan.lundstrom@ltu.se

Thomas Sandström

Department of Public Health and Clinical Medicine,Division of Medicine,  Umeå University, SE-90185, Umeå, Sweden

1

Corresponding author.

J. Fluids Eng 134(5), 051208 (May 22, 2012) (8 pages) doi:10.1115/1.4006698 History: Received September 07, 2011; Revised March 18, 2012; Published May 22, 2012; Online May 22, 2012

In this paper, we increase the understanding of the influence of the breathing pattern on the fate of inhaled non-spherical micro and nanoparticles and examine the accuracy of replacing the cyclic flow field with a quasi-steady flow. This is done with new analysis and numerical simulations on straight model airways using a previously developed discrete model for fiber motion. For the conditions studied, maximum deposition is obtained when fibers are released at the start of the inspiratory cycle, and minimum is received at the peak of inhalation. A quasi-steady solution generally provides a relatively good approximation to cyclic flow if an average velocity over one residence time of the particles moving with the mean fluid velocity is used. For a batch type, supply of particles deposition is favored in light activity breathing as compared to heavy breathing and the inclusion of a short pause after the inhalation results in an increased deposition in the terminal bronchiole. During zero-flow over the time of a breathing pause, spherical 10 nm particles experience considerable deposition in the distal airways, whereas only a few percent of larger and/ or fibrous nanoparticles were deposited. Hence, size and shape are crucial variables for deposition for no flow conditions. Common for all breathing parameters examined was that minimum deposition was obtained for the spherical 1 μm-particles and the fibrous 100 nm-particles. The former is expected from studies on spherical particles, and the latter is in agreement with results from a recent publication on steady inspiration.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Velocity profiles at nt = 0, π/8, π/4, π/2 for Weibel’s generation 0 (G0, α = 2.8) and 16 (G16, α = 0.1) at light activity breathing

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Figure 2

Inhaled volume versus time for light and heavy activity

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Figure 3

Deposition efficiency in Weibel’s G6 for fibers with β = 3 (left) and β = 100 (right) as a function of moment of fiber injection

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Figure 4

Deposition efficiency in Weibel’s G11 for fibers with β = 3 (left) and β = 100 (right) as a function of moment of fiber injection

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Figure 5

Deposition efficiency in Weibel’s G16 (α = 0.1) for fibers with β = 3 (left) and β = 100 (right) as a function of moment of fiber injection. Non-filled and gray symbols represent quasi-steady solution with initial and mean velocity approximation, respectively.

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