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Research Papers: Fundamental Issues and Canonical Flows

Modeling Transport and Deposition Efficiency of Oblate and Prolate Nano- and Micro-particles in a Virtual Model of the Human Airway

[+] Author and Article Information
Elise Holmstedt

Division of Fluid and Experimental Mechanics,
Luleå University of Technology,
Luleå SE-97 187, Sweden
e-mail: eliseh@ltu.se

Hans O. Åkerstedt, T. Staffan Lundström

Division of Fluid and Experimental Mechanics,
Luleå University of Technology,
Luleå SE-97 187, Sweden

Sofie M. Högberg

Sandvik Materials Technology,
Storgatan 2,
Sandviken SE-811 81, Sweden

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received April 28, 2015; final manuscript received February 3, 2016; published online May 2, 2016. Assoc. Editor: Daniel Maynes.

J. Fluids Eng 138(8), 081203 (May 02, 2016) (10 pages) Paper No: FE-15-1294; doi: 10.1115/1.4032934 History: Received April 28, 2015; Revised February 03, 2016

A model for the motion and deposition of oblate and prolate spheroids in the nano- and microscale was developed. The aim was to mimic the environment of the human lung, but the model is general and can be applied for different flows and geometries for small nonspherical particle Stokes and Reynolds numbers. A study of the motion and orientation of a single oblate and prolate particle has been done yielding that Brownian motion disturbs the Jeffery orbits for small particles. Prolate microparticles still display distinguishable orbits while oblate particles of the same size do not. A statistical study was done comparing the deposition efficiencies of oblate and prolate spheroids of different size and aspect ratio observing that smaller particles have higher deposition rate for lower aspect ratio while larger particles have higher deposition rates for large aspect ratio.

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Figures

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Fig. 1

A representative sketch of the geometry used in the simulations with the initial position for an oblate and a prolate particle in the single particle runs

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Fig. 2

Illustration of the spheroids used in the simulations: (a) oblate particle with polar semi-axis a and equatorial b and (b) prolate particle with polar semi-axis a and equatorial b

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Fig. 3

Euler angles connecting a particles local coordinates to the global ones [5]

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Fig. 4

Description of the motion of an oblate spheroid with df = 1 μm, β = 5 and in an airway of generation 4: (a) the rotation of one oblate particle plotted at regular intervals as it moves through an airway and (b) the angles, q and f, describing the rotation of the oblate particle

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Fig. 5

Description of the motion of a prolate spheroid with df = 1 μm, β = 5 and in an airway of generation 4: (a) the rotation of one prolate particle plotted at regular intervals as it moves through an airway and (b) the angles, q and f, describing the rotation of the prolate particle

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Fig. 6

Similar setup as in Fig. 4 but with Brownian motion included: (a) snapshots of an oblate particle as it moves through the airway and (b) the angular positions of an oblate particle

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Fig. 7

Similar setup as in Fig. 5 but with Brownian motion included: (a) snapshots of a prolate particle as it moves through the airway and (b) the angular positions of a prolate particle

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Fig. 8

Simulations of particles with a fixed aspect ratio of β = 100, but with a varied geometric diameter so that the oblate and prolate particle volumes are comparable

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Fig. 9

Deposition efficiencies for each generation as particles pass through the complete model of the lung: (a) deposition of oblate spheroids in a multigenerational model of a lung and (b) deposition of prolate spheroids in a multigenerational model of a lung

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Fig. 10

Simulations of depositions of particles with changed aspect ratio. Plotted on a logarithmic scale with the inverse of β for the prolate particles: (a) minor axis of 46 nm, (b) minor axis of 100 nm, (c) minor axis of 460 nm, and (d) minor axis of 1 μm.

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