---
_id: '9728'
abstract:
- lang: eng
text: "Most real-world flows are multiphase, yet we know little about them compared
to their single-phase counterparts. Multiphase flows are more difficult to investigate
as their dynamics occur in large parameter space and involve complex phenomena
such as preferential concentration, turbulence modulation, non-Newtonian rheology,
etc. Over the last few decades, experiments in particle-laden flows have taken
a back seat in favour of ever-improving computational resources. However, computers
are still not powerful enough to simulate a real-world fluid with millions of
finite-size particles. Experiments are essential not only because they offer a
reliable way to investigate real-world multiphase flows but also because they
serve to validate numerical studies and steer the research in a relevant direction.
In this work, we have experimentally investigated particle-laden flows in pipes,
and in particular, examined the effect of particles on the laminar-turbulent transition
and the drag scaling in turbulent flows.\r\n\r\nFor particle-laden pipe flows,
an earlier study [Matas et al., 2003] reported how the sub-critical (i.e., hysteretic)
transition that occurs via localised turbulent structures called puffs is affected
by the addition of particles. In this study, in addition to this known transition,
we found a super-critical transition to a globally fluctuating state with increasing
particle concentration. At the same time, the Newtonian-type transition via puffs
is delayed to larger Reynolds numbers. At an even higher concentration, only the
globally fluctuating state is found. The dynamics of particle-laden flows are
hence determined by two competing instabilities that give rise to three flow regimes:
Newtonian-type turbulence at low, a particle-induced globally fluctuating state
at high, and a coexistence state at intermediate concentrations.\r\n\r\nThe effect
of particles on turbulent drag is ambiguous, with studies reporting drag reduction,
no net change, and even drag increase. The ambiguity arises because, in addition
to particle concentration, particle shape, size, and density also affect the net
drag. Even similar particles might affect the flow dissimilarly in different Reynolds
number and concentration ranges. In the present study, we explored a wide range
of both Reynolds number and concentration, using spherical as well as cylindrical
particles. We found that the spherical particles do not reduce drag while the
cylindrical particles are drag-reducing within a specific Reynolds number interval.
The interval strongly depends on the particle concentration and the relative size
of the pipe and particles. Within this interval, the magnitude of drag reduction
reaches a maximum. These drag reduction maxima appear to fall onto a distinct
power-law curve irrespective of the pipe diameter and particle concentration,
and this curve can be considered as the maximum drag reduction asymptote for a
given fibre shape. Such an asymptote is well known for polymeric flows but had
not been identified for particle-laden flows prior to this work."
acknowledged_ssus:
- _id: M-Shop
alternative_title:
- ISTA Thesis
article_processing_charge: No
author:
- first_name: Nishchal
full_name: Agrawal, Nishchal
id: 469E6004-F248-11E8-B48F-1D18A9856A87
last_name: Agrawal
citation:
ama: Agrawal N. Transition to turbulence and drag reduction in particle-laden pipe
flows. 2021. doi:10.15479/at:ista:9728
apa: Agrawal, N. (2021). Transition to turbulence and drag reduction in particle-laden
pipe flows. Institute of Science and Technology Austria. https://doi.org/10.15479/at:ista:9728
chicago: Agrawal, Nishchal. “Transition to Turbulence and Drag Reduction in Particle-Laden
Pipe Flows.” Institute of Science and Technology Austria, 2021. https://doi.org/10.15479/at:ista:9728.
ieee: N. Agrawal, “Transition to turbulence and drag reduction in particle-laden
pipe flows,” Institute of Science and Technology Austria, 2021.
ista: Agrawal N. 2021. Transition to turbulence and drag reduction in particle-laden
pipe flows. Institute of Science and Technology Austria.
mla: Agrawal, Nishchal. Transition to Turbulence and Drag Reduction in Particle-Laden
Pipe Flows. Institute of Science and Technology Austria, 2021, doi:10.15479/at:ista:9728.
short: N. Agrawal, Transition to Turbulence and Drag Reduction in Particle-Laden
Pipe Flows, Institute of Science and Technology Austria, 2021.
date_created: 2021-07-27T13:40:30Z
date_published: 2021-07-29T00:00:00Z
date_updated: 2024-02-28T13:14:39Z
day: '29'
ddc:
- '532'
degree_awarded: PhD
department:
- _id: GradSch
- _id: BjHo
doi: 10.15479/at:ista:9728
file:
- access_level: closed
checksum: 77436be3563a90435024307b1b5ee7e8
content_type: application/x-zip-compressed
creator: nagrawal
date_created: 2021-07-28T13:32:02Z
date_updated: 2022-07-29T22:30:05Z
embargo_to: open_access
file_id: '9744'
file_name: Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows.zip
file_size: 22859658
relation: source_file
- access_level: open_access
checksum: 72a891d7daba85445c29b868c22575ed
content_type: application/pdf
creator: nagrawal
date_created: 2021-07-28T13:32:05Z
date_updated: 2022-07-29T22:30:05Z
embargo: 2022-07-28
file_id: '9745'
file_name: Transition to Turbulence and Drag Reduction in Particle-Laden Pipe Flows.pdf
file_size: 18658048
relation: main_file
file_date_updated: 2022-07-29T22:30:05Z
has_accepted_license: '1'
keyword:
- Drag Reduction
- Transition to Turbulence
- Multiphase Flows
- particle Laden Flows
- Complex Flows
- Experiments
- Fluid Dynamics
language:
- iso: eng
license: https://creativecommons.org/licenses/by/4.0/
month: '07'
oa: 1
oa_version: Published Version
page: '118'
publication_identifier:
issn:
- 2663-337X
publication_status: published
publisher: Institute of Science and Technology Austria
related_material:
record:
- id: '6189'
relation: part_of_dissertation
status: public
status: public
supervisor:
- first_name: Björn
full_name: Hof, Björn
id: 3A374330-F248-11E8-B48F-1D18A9856A87
last_name: Hof
orcid: 0000-0003-2057-2754
title: Transition to turbulence and drag reduction in particle-laden pipe flows
tmp:
image: /images/cc_by.png
legal_code_url: https://creativecommons.org/licenses/by/4.0/legalcode
name: Creative Commons Attribution 4.0 International Public License (CC-BY 4.0)
short: CC BY (4.0)
type: dissertation
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
year: '2021'
...
---
_id: '6189'
abstract:
- lang: eng
text: 'Suspended particles can alter the properties of fluids and in particular
also affect the transition fromlaminar to turbulent flow. An earlier study [Mataset
al.,Phys. Rev. Lett.90, 014501 (2003)] reported howthe subcritical (i.e., hysteretic)
transition to turbulent puffs is affected by the addition of particles. Here weshow
that in addition to this known transition, with increasing concentration a supercritical
(i.e.,continuous) transition to a globally fluctuating state is found. At the
same time the Newtonian-typetransition to puffs is delayed to larger Reynolds
numbers. At even higher concentration only the globallyfluctuating state is found.
The dynamics of particle laden flows are hence determined by two competinginstabilities
that give rise to three flow regimes: Newtonian-type turbulence at low, a particle
inducedglobally fluctuating state at high, and a coexistence state at intermediate
concentrations.'
article_number: '114502'
article_processing_charge: No
author:
- first_name: Nishchal
full_name: Agrawal, Nishchal
id: 469E6004-F248-11E8-B48F-1D18A9856A87
last_name: Agrawal
- first_name: George H
full_name: Choueiri, George H
id: 448BD5BC-F248-11E8-B48F-1D18A9856A87
last_name: Choueiri
- first_name: Björn
full_name: Hof, Björn
id: 3A374330-F248-11E8-B48F-1D18A9856A87
last_name: Hof
orcid: 0000-0003-2057-2754
citation:
ama: Agrawal N, Choueiri GH, Hof B. Transition to turbulence in particle laden flows.
Physical Review Letters. 2019;122(11). doi:10.1103/PhysRevLett.122.114502
apa: Agrawal, N., Choueiri, G. H., & Hof, B. (2019). Transition to turbulence
in particle laden flows. Physical Review Letters. American Physical Society.
https://doi.org/10.1103/PhysRevLett.122.114502
chicago: Agrawal, Nishchal, George H Choueiri, and Björn Hof. “Transition to Turbulence
in Particle Laden Flows.” Physical Review Letters. American Physical Society,
2019. https://doi.org/10.1103/PhysRevLett.122.114502.
ieee: N. Agrawal, G. H. Choueiri, and B. Hof, “Transition to turbulence in particle
laden flows,” Physical Review Letters, vol. 122, no. 11. American Physical
Society, 2019.
ista: Agrawal N, Choueiri GH, Hof B. 2019. Transition to turbulence in particle
laden flows. Physical Review Letters. 122(11), 114502.
mla: Agrawal, Nishchal, et al. “Transition to Turbulence in Particle Laden Flows.”
Physical Review Letters, vol. 122, no. 11, 114502, American Physical Society,
2019, doi:10.1103/PhysRevLett.122.114502.
short: N. Agrawal, G.H. Choueiri, B. Hof, Physical Review Letters 122 (2019).
date_created: 2019-03-31T21:59:12Z
date_published: 2019-03-22T00:00:00Z
date_updated: 2024-03-28T23:30:48Z
day: '22'
department:
- _id: BjHo
doi: 10.1103/PhysRevLett.122.114502
external_id:
arxiv:
- '1809.06358'
isi:
- '000461922000006'
intvolume: ' 122'
isi: 1
issue: '11'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/1809.06358
month: '03'
oa: 1
oa_version: Preprint
publication: Physical Review Letters
publication_identifier:
eissn:
- '10797114'
issn:
- '00319007'
publication_status: published
publisher: American Physical Society
quality_controlled: '1'
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- id: '9728'
relation: dissertation_contains
status: public
scopus_import: '1'
status: public
title: Transition to turbulence in particle laden flows
type: journal_article
user_id: 2DF688A6-F248-11E8-B48F-1D18A9856A87
volume: 122
year: '2019'
...