Experimental study of negatively buoyant finite-size particles in a turbulent boundary layer up to dense regimes
dc.contributor.author
Baker, Lucia J.
dc.contributor.author
Coletti, Filippo
dc.date.accessioned
2021-08-24T09:03:48Z
dc.date.available
2021-08-20T12:28:05Z
dc.date.available
2021-08-24T09:03:48Z
dc.date.issued
2019-05-10
dc.identifier.issn
0022-1120
dc.identifier.issn
1469-7645
dc.identifier.other
10.1017/jfm.2019.99
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/501607
dc.description.abstract
We experimentally investigate the two-phase interplay in an open-channel turbulent boundary layer laden with finite-size particles at global volume fractions between 4 and 25 %. The working fluid (water) and the dispersed phase (hydrogel spheres) have closely matched refractive indices, allowing us to measure the properties of both phases using particle image velocimetry and particle tracking velocimetry, respectively. The particles have a diameter of approximately 9 % of the channel depth and are slightly denser than the fluid. The negative buoyancy causes a strong vertical concentration gradient, characterized by discrete and closely spaced particle layers parallel to the wall. Even at the lowest considered volume fractions, the near-wall fluid velocity and velocity gradients are strongly reduced, with large mean shear throughout most of the channel height. This indicates that the local effective viscosity of the suspension is greatly increased due to the friction between particle layers sliding over one another. The particles consistently lag the fluid and leave their footprint on its mean and fluctuating velocity profiles. The turbulent activity is damped near the wall, where the nearly packed particles disrupt and suppress large-scale turbulent fluctuations and redistribute some of the kinetic energy to smaller scales. On the other hand, in the outer region of the flow where the local particle concentration is low, the mean shear produces strong Reynolds stresses, with enhanced sweeps and ejections and frequent swirling events.
en_US
dc.language.iso
en
en_US
dc.publisher
Cambridge University Press
en_US
dc.title
Experimental study of negatively buoyant finite-size particles in a turbulent boundary layer up to dense regimes
en_US
dc.type
Journal Article
dc.date.published
2019-03-13
ethz.journal.title
Journal of Fluid Mechanics
ethz.journal.volume
866
en_US
ethz.journal.abbreviated
J. Fluid Mech.
ethz.pages.start
598
en_US
ethz.pages.end
629
en_US
ethz.publication.place
Cambridge
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02628 - Institut für Fluiddynamik / Institute of Fluid Dynamics::09709 - Coletti, Filippo / Coletti, Filippo
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02628 - Institut für Fluiddynamik / Institute of Fluid Dynamics::09709 - Coletti, Filippo / Coletti, Filippo
en_US
ethz.date.deposited
2021-08-20T12:28:10Z
ethz.source
FORM
ethz.eth
no
en_US
ethz.availability
Metadata only
en_US
ethz.rosetta.installDate
2021-08-24T09:03:54Z
ethz.rosetta.lastUpdated
2021-08-24T09:03:54Z
ethz.rosetta.versionExported
true
ethz.COinS
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