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Modelling Transport of Non-Spherical Particles in Small Channel Flow
Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A model has been developed to predict the movement of oblate and prolate particles on amicro- and nano-scale in laminar channel flow, both for purposes of statistical aggregationand to study motion of single particles. For the purpose of this thesis the model has beenadapted to examine particle deposition patterns in the human lung and the filtration ofparticles during manufacturing of composites, but the possibilities of the model extendto all areas where the particle Stokes and Reynolds numbers are small.To examine the influence the breathing pattern has on the deposition of inhalednano- and micro-fibres deposition rates were compared at different injection points ofthe breathing cycle, where maximum deposition was found when the particles releasedat the beginning of the respiratory cycle while minimum deposition occurred when therelease came at peak inhalation. A comparison between a quasi-steady flow and a cyclicflow was done and it was found that a quasi-steady solution provides a reasonably goodapproximation if the velocity used is a mean of the velocity during the residence time ofthe simulations.A statistical study was done to compare the deposition rates of oblate and prolateparticles of different size and aspect ratio as they travel down narrowing bronchi in asteady, fully developed parabolic flow field. The model shows a clear correlation betweenincreased particle size and increased deposition, it also consistently yielded a higherdeposition rate for oblate particles compared to prolate particles with a similar geometricdiameter. A study of the motion and orientation of single oblate and prolate particleswith large aspect ratio and the same geometric diameter has also been done.In liquid moulding of fibre reinforced composites the resin can be enhanced by nanoandmicro-particles to give the final product additional properties. This is a processthat can be simulated by approximating the gap formed between the fibre bundles to achannel flow with a radially suctioning component caused by the capillary pressure in themicro channels in the bundles. First this flow field is described with a radial componentthat is constant over the length of the channel and compared with a flow purely drivenby an applied pressure gradient without radial forces. Particle size showed a small butstill noticeable influence, particularly for larger particles under the influence of gravity.The second flow field used is time dependent where the flow front in the bundlesand channel mimics that of previous observations. There is initially a period where theflow front in the channel is leading but the radial capillary fluid transport causes thisto retreat and be overtaken by the flow front in the bundles. Particles mixed in theresin will in general travel with a velocity greater than that of the fluid front until theradial velocity component at that point filters the particles by transporting them to thechannel wall. Particle geometry has a smaller impact on the deposition rates in compositemanufacturing than in inhalation since the effect of Brownian forces and gravity are muchsmaller, although there is still some discernible patterns such as a higher deposition ratefor spherical particles during the transport to the flow front.

Place, publisher, year, edition, pages
Luleå University of Technology, 2016. , 122 p.
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-60402ISBN: 978-91-7583-765-9ISBN: 978-91-7583-766-6 (pdf)OAI: oai:DiVA.org:ltu-60402DiVA: diva2:1046615
Public defence
2016-12-16, E632, Luleå tekniska universitet, 09:00
Opponent
Supervisors
Available from: 2016-11-15 Created: 2016-11-14 Last updated: 2016-11-28Bibliographically approved
List of papers
1. Modeling Transport and Deposition Efficiency of Oblate and Prolate Nano- and Micro-particles in a Virtual Model of the Human Airway
Open this publication in new window or tab >>Modeling Transport and Deposition Efficiency of Oblate and Prolate Nano- and Micro-particles in a Virtual Model of the Human Airway
2016 (English)In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 138, no 8, 81203Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Fluid Mechanics and Acoustics
Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-11039 (URN)10.1115/1.4032934 (DOI)9f112cec-8570-4373-955e-d6f548e3c363 (Local ID)9f112cec-8570-4373-955e-d6f548e3c363 (Archive number)9f112cec-8570-4373-955e-d6f548e3c363 (OAI)
Note

Validerad; 2016; Nivå 2; 20160816 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2016-11-23Bibliographically approved
2. Time-dependent deposition of micro- and nanofibers in straight model airways
Open this publication in new window or tab >>Time-dependent deposition of micro- and nanofibers in straight model airways
Show others...
2012 (English)In: Journal of Fluids Engineering - Trancactions of The ASME, ISSN 0098-2202, E-ISSN 1528-901X, Vol. 134, no 5, 051208-1 p.Article in journal (Refereed) Published
Abstract [en]

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.

Research subject
Fluid Mechanics
Identifiers
urn:nbn:se:ltu:diva-4893 (URN)10.1115/1.4006698 (DOI)2e48b609-305f-4617-b4c8-861700e18519 (Local ID)2e48b609-305f-4617-b4c8-861700e18519 (Archive number)2e48b609-305f-4617-b4c8-861700e18519 (OAI)
Note
Validerad; 2012; 20120314 (stlu)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2016-11-14Bibliographically approved

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