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Inertial migration of spherical and oblate particles in straight ducts
KTH, Skolan för teknikvetenskap (SCI), Mekanik.ORCID-id: 0000-0002-0122-401X
KTH, Centra, SeRC - Swedish e-Science Research Centre. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.ORCID-id: 0000-0003-4328-7921
KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
KTH, Skolan för bioteknologi (BIO), Proteomik och nanobioteknologi.
Vise andre og tillknytning
(engelsk)Inngår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645Artikkel i tidsskrift (Fagfellevurdert) Accepted
Abstract [en]

We study numerically the inertial migration of a single rigid sphere and an oblate spheroid in straight square and rectangular ducts. A highly accurate interface-resolved numerical algorithm is employed to analyse the entire migration dynamics of the oblate particle and compare it with that of the sphere. Similarly to the inertial focusing of spheres, the oblate particle reaches one of the four face-centred equilibrium positions, however they are vertically aligned with the axis of symmetry in the spanwise direction. In addition, the lateral trajectories of spheres and oblates collapse into an equilibrium manifold before ending at the equilibrium positions, with the equilibrium manifold tangential to lines of constant background shear for both sphere and oblate particles. The differences between the migration of the oblate and sphere are also presented, in particular the oblate may focus on the diagonal symmetry line of the duct cross-section, close to one of the corners, if its diameter is larger than a certain threshold. Moreover, we show that the final orientation and rotation of the oblate exhibit a chaotic behaviour for Reynolds numbers beyond a critical value. Finally, we document that the lateral motion of the oblate particle is less uniform than that of the spherical particle due to its evident tumbling motion throughout the migration. In a square duct, the strong tumbling motion of the oblate in the first stage of the migration results in a lower lateral velocity and consequently longer focusing length with respect to that of the spherical particle. The opposite is true in a rectangular duct where the higher lateral velocity of the oblate in the second stage of the migration, with negligible tumbling, gives rise to shorter focusing lengths.These results can help the design of microfluidic systems for bio-applications.

HSV kategori
Identifikatorer
URN: urn:nbn:se:kth:diva-204162DOI: 10.1017/jfm.2017.189ISI: 000405373500005Scopus ID: 2-s2.0-85018317724OAI: oai:DiVA.org:kth-204162DiVA, id: diva2:1084197
Merknad

QC 20170328

Tilgjengelig fra: 2017-03-23 Laget: 2017-03-23 Sist oppdatert: 2019-02-28bibliografisk kontrollert
Inngår i avhandling
1. Numerical study of non-spherical/spherical particles in laminar and turbulent flows
Åpne denne publikasjonen i ny fane eller vindu >>Numerical study of non-spherical/spherical particles in laminar and turbulent flows
2017 (engelsk)Licentiatavhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The presence of solid rigid particles alters the global transport and rheological properties of the mixture in complex (and often unpredictable) ways. In recent years a few studies have been devoted to investigating the behavior of dense suspensions in the turbulent/inertial regime with the majority of theses analyses limited to mono-disperse rigid neutrally-buoyant spheres. However, one interesting parameter that is rarely studied for particles with high inertia is the particle shape. Spheroidal particles introduce an anisotropy, e.g. a tendency to orient in a certain direction, which can affect the bulk behavior of a suspension in an unexpected ways. The main focus of this study is therefore to investigate the behavior of spheroidal particles and their effect on turbulent/inertial flows.

We perform fully resolved simulations of particulate flows with spherical/spheroidal particles, using an efficient/accurate numerical approach that enables us to simulate thousands of particles with high resolutions in order to capture all the fluid-solid interactions.

Several conclusions are drawn from this study that reveal the importance of particle's shape effect on the behaviour of a suspension e.g. spheroidal particles tend to cluster while sedimenting. This phenomenon is observed in this work for both particles with high inertia, sedimenting in a quiescent fluid and inertialess particles (point-like tracer prolates) settling in homogenous isotropic turbulence. The mechanisms for clustering is indeed different between these two situations, however, it is the shape of particles that governs these mechanisms, as clustering is not observed for spherical particles. Another striking finding of this work is drag reduction in particulate turbulent channel flow with rigid oblate particles. Again this drag reduction is absent for spherical particles, which instead increase the drag with respect to single-phase turbulence. 

sted, utgiver, år, opplag, sider
KTH Royal Institute of Technology, 2017. s. 31
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-204421 (URN)978-91-7729-333-0 (ISBN)
Presentation
2017-04-20, E51, Osquars backe 14, Stockholm, 14:00 (engelsk)
Opponent
Veileder
Merknad

QC 20170328

Tilgjengelig fra: 2017-03-28 Laget: 2017-03-24 Sist oppdatert: 2017-03-28bibliografisk kontrollert
2. Numerical study of transport phenomena in particle suspensions
Åpne denne publikasjonen i ny fane eller vindu >>Numerical study of transport phenomena in particle suspensions
2019 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

Suspensions of solid particles in a viscous liquid are of scientific and technological interest in a wide range of applications. Sediment transport in estuaries, blood flow in the human body, pyroclastic flows from volcanos and pulp fibers in papermaking are among the examples. Often, these particulate flows also include heat transfer among the two phases or the fluid might exhibit a viscoelastic behavior. Predicting these flows and the heat transfer within requires a vast knowledge of how particles are distributed across the domain, how particles affect the flow field and finally how they affect the global behavior of the suspension. The aim of this work is therefore to improve the physical understanding of these flows, including the effect of physical and mechanical properties of the particles and the domain that bounds them.To this purpose, particle-resolved direct numerical simulations (PR-DNS) of spherical/non-spherical particles in different flow regimes and geometries are performed, using an efficient/accurate numerical tool that is developed within this work. The code is based on the Immersed Boundary Method (IBM) for the fluid-solid interactions with lubrication, friction and collision models for the close range particle-particle (particle-wall) interactions, also able to resolve for heat transfer equation in both Newtonian and non-Newtonian fluids.

Several conclusions are drawn from this study, revealing the importance of the particle's shape and inertia on the global behavior of a suspension, e.g. spheroidal particles tend to cluster while sedimenting. This phenomenon is observed here for both particles with high inertia, sedimenting in a quiescent fluid and inertialess particles (point-like tracer prolates) settling in homogeneous isotropic turbulence. The mechanisms for clustering is indeed different between these two situations, however, it is the shape of the particles that governs these mechanisms, as clustering is not observed for spherical particles. Another striking finding of this work is drag reduction in particulate turbulent channel flow with disk-like spheroidal particles. Again this drag reduction is absent for spherical particles, which instead increase the drag with respect to single-phase turbulence. In particular, we show that inertia at the particle scale induces a non-linear increase of the heat transfer as a function of the volume fraction, unlike the case at vanishing inertia where heat transfer increases linearly within the suspension.

sted, utgiver, år, opplag, sider
KTH Royal Institute of Technology, 2019. s. 63
Serie
TRITA-MEK, ISSN 0348-467X ; 2019:03
HSV kategori
Forskningsprogram
Teknisk mekanik
Identifikatorer
urn:nbn:se:kth:diva-240126 (URN)978-91-7873-065-0 (ISBN)
Disputas
2019-01-25, H1, Teknikringen 33, våningsplan 5, H-huset, KTH Campus, Stockholm, 10:30 (engelsk)
Opponent
Veileder
Forskningsfinansiär
EU, European Research Council, ERC-2013-CoG-616186, TRITOS
Tilgjengelig fra: 2018-12-13 Laget: 2018-12-12 Sist oppdatert: 2018-12-13bibliografisk kontrollert
3. Point of care microfluidic tool development for resource limited settings
Åpne denne publikasjonen i ny fane eller vindu >>Point of care microfluidic tool development for resource limited settings
2019 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The development of point of care diagnostics using recent advances in microfluidics have the potential to transform health care in several ways, especially in resource limited settings with limited access to advanced health care infrastructure. However, translating a point of care device to reality is often a challenging task because of the complexities involved in integrating a number of diverse engineering concepts into an easy to use, accurate and portable device. This thesis focuses on miniaturization of crucial diagnostic laboratory tools, that can be used in a portable point of care format without compromising on the accuracy or performance. The first part of the thesis (Paper I-III) focuses on understanding and applying elasto-inertial microfluidics, which is a label-free and passive bio-particle sorting and separation method. A basic understanding of particle trajectories in both inertial (Paper I) and visco-elastic flows (Paper II) is established, followed by an investigation on the combined effects of inertia and elasticity (Paper III). The second part of the thesis (Paper IV-VI) focuses on developing integrated microfluidic platforms, each of which addresses different aspects of point of care diagnostic applications. The applications include neonatal diagnostics using a hand-driven Slipdisc technique (Paper IV), rapid nucleic acid quantification using a novel precipitate-based detection on a centrifugal microfluidics platform (Paper V), and hematocrit level measurement in blood using a portable lab-on- Disc platform operated by a mobile phone (Paper VI). The proof of concept microfluidic tools presented in the scope of this thesis have the potential to replace a number of functions of standard laboratory equipment, at a fraction of the price and without compromising performance. Hence, the different methods developed should contribute towards decentralization of medical testing laboratories, making healthcare accessible to one and all.

sted, utgiver, år, opplag, sider
Stockholm: KTH Royal Institute of Technology, 2019. s. 63
Serie
TRITA-CBH-FOU ; 2019:15
Emneord
Blood, control, cell separation, centrifugal microfluidics, diagnostics, elasto-inertial, hematocrit level, microfluidics, neonatal diagnostics, nucleic acid quantification, point of care, particle focusing, resource limited settings.
HSV kategori
Forskningsprogram
Bioteknologi
Identifikatorer
urn:nbn:se:kth:diva-244825 (URN)978-91-7873-122-0 (ISBN)
Disputas
2019-03-29, Air & Fire auditorium, Science for Life Laboratory, Tomtebodavägen 23, Solna, 10:00 (engelsk)
Opponent
Veileder
Merknad

QC 20190228

Tilgjengelig fra: 2019-02-28 Laget: 2019-02-28 Sist oppdatert: 2019-02-28bibliografisk kontrollert

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