---
_id: '7932'
abstract:
- lang: eng
text: Pulsating flows through tubular geometries are laminar provided that velocities
are moderate. This in particular is also believed to apply to cardiovascular flows
where inertial forces are typically too low to sustain turbulence. On the other
hand, flow instabilities and fluctuating shear stresses are held responsible for
a variety of cardiovascular diseases. Here we report a nonlinear instability mechanism
for pulsating pipe flow that gives rise to bursts of turbulence at low flow rates.
Geometrical distortions of small, yet finite, amplitude are found to excite a
state consisting of helical vortices during flow deceleration. The resulting flow
pattern grows rapidly in magnitude, breaks down into turbulence, and eventually
returns to laminar when the flow accelerates. This scenario causes shear stress
fluctuations and flow reversal during each pulsation cycle. Such unsteady conditions
can adversely affect blood vessels and have been shown to promote inflammation
and dysfunction of the shear stress-sensitive endothelial cell layer.
article_processing_charge: No
article_type: original
arxiv: 1
author:
- first_name: Duo
full_name: Xu, Duo
id: 3454D55E-F248-11E8-B48F-1D18A9856A87
last_name: Xu
- first_name: Atul
full_name: Varshney, Atul
id: 2A2006B2-F248-11E8-B48F-1D18A9856A87
last_name: Varshney
orcid: 0000-0002-3072-5999
- first_name: Xingyu
full_name: Ma, Xingyu
id: 34BADBA6-F248-11E8-B48F-1D18A9856A87
last_name: Ma
orcid: 0000-0002-0179-9737
- first_name: Baofang
full_name: Song, Baofang
last_name: Song
- first_name: Michael
full_name: Riedl, Michael
id: 3BE60946-F248-11E8-B48F-1D18A9856A87
last_name: Riedl
orcid: 0000-0003-4844-6311
- first_name: Marc
full_name: Avila, Marc
last_name: Avila
- first_name: Björn
full_name: Hof, Björn
id: 3A374330-F248-11E8-B48F-1D18A9856A87
last_name: Hof
orcid: 0000-0003-2057-2754
citation:
ama: Xu D, Varshney A, Ma X, et al. Nonlinear hydrodynamic instability and turbulence
in pulsatile flow. Proceedings of the National Academy of Sciences of the United
States of America. 2020;117(21):11233-11239. doi:10.1073/pnas.1913716117
apa: Xu, D., Varshney, A., Ma, X., Song, B., Riedl, M., Avila, M., & Hof, B.
(2020). Nonlinear hydrodynamic instability and turbulence in pulsatile flow. Proceedings
of the National Academy of Sciences of the United States of America. National
Academy of Sciences. https://doi.org/10.1073/pnas.1913716117
chicago: Xu, Duo, Atul Varshney, Xingyu Ma, Baofang Song, Michael Riedl, Marc Avila,
and Björn Hof. “Nonlinear Hydrodynamic Instability and Turbulence in Pulsatile
Flow.” Proceedings of the National Academy of Sciences of the United States
of America. National Academy of Sciences, 2020. https://doi.org/10.1073/pnas.1913716117.
ieee: D. Xu et al., “Nonlinear hydrodynamic instability and turbulence in
pulsatile flow,” Proceedings of the National Academy of Sciences of the United
States of America, vol. 117, no. 21. National Academy of Sciences, pp. 11233–11239,
2020.
ista: Xu D, Varshney A, Ma X, Song B, Riedl M, Avila M, Hof B. 2020. Nonlinear hydrodynamic
instability and turbulence in pulsatile flow. Proceedings of the National Academy
of Sciences of the United States of America. 117(21), 11233–11239.
mla: Xu, Duo, et al. “Nonlinear Hydrodynamic Instability and Turbulence in Pulsatile
Flow.” Proceedings of the National Academy of Sciences of the United States
of America, vol. 117, no. 21, National Academy of Sciences, 2020, pp. 11233–39,
doi:10.1073/pnas.1913716117.
short: D. Xu, A. Varshney, X. Ma, B. Song, M. Riedl, M. Avila, B. Hof, Proceedings
of the National Academy of Sciences of the United States of America 117 (2020)
11233–11239.
date_created: 2020-06-07T22:00:51Z
date_published: 2020-05-26T00:00:00Z
date_updated: 2023-11-30T10:55:13Z
day: '26'
department:
- _id: BjHo
doi: 10.1073/pnas.1913716117
ec_funded: 1
external_id:
arxiv:
- '2005.11190'
isi:
- '000536797100014'
intvolume: ' 117'
isi: 1
issue: '21'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/2005.11190
month: '05'
oa: 1
oa_version: Preprint
page: 11233-11239
project:
- _id: 238B8092-32DE-11EA-91FC-C7463DDC885E
call_identifier: FWF
grant_number: I04188
name: Instabilities in pulsating pipe flow of Newtonian and complex fluids
- _id: 260C2330-B435-11E9-9278-68D0E5697425
call_identifier: H2020
grant_number: '754411'
name: ISTplus - Postdoctoral Fellowships
publication: Proceedings of the National Academy of Sciences of the United States
of America
publication_identifier:
eissn:
- '10916490'
issn:
- '00278424'
publication_status: published
publisher: National Academy of Sciences
quality_controlled: '1'
related_material:
link:
- description: News on IST Homepage
relation: press_release
url: https://ist.ac.at/en/news/blood-flows-more-turbulent-than-previously-expected/
record:
- id: '12726'
relation: dissertation_contains
status: public
- id: '14530'
relation: dissertation_contains
status: public
scopus_import: '1'
status: public
title: Nonlinear hydrodynamic instability and turbulence in pulsatile flow
type: journal_article
user_id: 4359f0d1-fa6c-11eb-b949-802e58b17ae8
volume: 117
year: '2020'
...
---
_id: '745'
abstract:
- lang: eng
text: 'Fluid flows in nature and applications are frequently subject to periodic
velocity modulations. Surprisingly, even for the generic case of flow through
a straight pipe, there is little consensus regarding the influence of pulsation
on the transition threshold to turbulence: while most studies predict a monotonically
increasing threshold with pulsation frequency (i.e. Womersley number, ), others
observe a decreasing threshold for identical parameters and only observe an increasing
threshold at low . In the present study we apply recent advances in the understanding
of transition in steady shear flows to pulsating pipe flow. For moderate pulsation
amplitudes we find that the first instability encountered is subcritical (i.e.
requiring finite amplitude disturbances) and gives rise to localized patches of
turbulence (''puffs'') analogous to steady pipe flow. By monitoring the impact
of pulsation on the lifetime of turbulence we map the onset of turbulence in parameter
space. Transition in pulsatile flow can be separated into three regimes. At small
Womersley numbers the dynamics is dominated by the decay turbulence suffers during
the slower part of the cycle and hence transition is delayed significantly. As
shown in this regime thresholds closely agree with estimates based on a quasi-steady
flow assumption only taking puff decay rates into account. The transition point
predicted in the zero limit equals to the critical point for steady pipe flow
offset by the oscillation Reynolds number (i.e. the dimensionless oscillation
amplitude). In the high frequency limit on the other hand, puff lifetimes are
identical to those in steady pipe flow and hence the transition threshold appears
to be unaffected by flow pulsation. In the intermediate frequency regime the transition
threshold sharply drops (with increasing ) from the decay dominated (quasi-steady)
threshold to the steady pipe flow level.'
article_processing_charge: No
author:
- first_name: Duo
full_name: Xu, Duo
id: 3454D55E-F248-11E8-B48F-1D18A9856A87
last_name: Xu
- first_name: Sascha
full_name: Warnecke, Sascha
last_name: Warnecke
- first_name: Baofang
full_name: Song, Baofang
last_name: Song
- first_name: Xingyu
full_name: Ma, Xingyu
id: 34BADBA6-F248-11E8-B48F-1D18A9856A87
last_name: Ma
orcid: 0000-0002-0179-9737
- first_name: Björn
full_name: Hof, Björn
id: 3A374330-F248-11E8-B48F-1D18A9856A87
last_name: Hof
orcid: 0000-0003-2057-2754
citation:
ama: Xu D, Warnecke S, Song B, Ma X, Hof B. Transition to turbulence in pulsating
pipe flow. Journal of Fluid Mechanics. 2017;831:418-432. doi:10.1017/jfm.2017.620
apa: Xu, D., Warnecke, S., Song, B., Ma, X., & Hof, B. (2017). Transition to
turbulence in pulsating pipe flow. Journal of Fluid Mechanics. Cambridge
University Press. https://doi.org/10.1017/jfm.2017.620
chicago: Xu, Duo, Sascha Warnecke, Baofang Song, Xingyu Ma, and Björn Hof. “Transition
to Turbulence in Pulsating Pipe Flow.” Journal of Fluid Mechanics. Cambridge
University Press, 2017. https://doi.org/10.1017/jfm.2017.620.
ieee: D. Xu, S. Warnecke, B. Song, X. Ma, and B. Hof, “Transition to turbulence
in pulsating pipe flow,” Journal of Fluid Mechanics, vol. 831. Cambridge
University Press, pp. 418–432, 2017.
ista: Xu D, Warnecke S, Song B, Ma X, Hof B. 2017. Transition to turbulence in pulsating
pipe flow. Journal of Fluid Mechanics. 831, 418–432.
mla: Xu, Duo, et al. “Transition to Turbulence in Pulsating Pipe Flow.” Journal
of Fluid Mechanics, vol. 831, Cambridge University Press, 2017, pp. 418–32,
doi:10.1017/jfm.2017.620.
short: D. Xu, S. Warnecke, B. Song, X. Ma, B. Hof, Journal of Fluid Mechanics 831
(2017) 418–432.
date_created: 2018-12-11T11:48:17Z
date_published: 2017-11-25T00:00:00Z
date_updated: 2023-09-27T12:28:12Z
day: '25'
department:
- _id: BjHo
doi: 10.1017/jfm.2017.620
ec_funded: 1
external_id:
isi:
- '000412934800005'
intvolume: ' 831'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/1709.03738
month: '11'
oa: 1
oa_version: Submitted Version
page: 418 - 432
project:
- _id: 25152F3A-B435-11E9-9278-68D0E5697425
call_identifier: FP7
grant_number: '306589'
name: Decoding the complexity of turbulence at its origin
publication: Journal of Fluid Mechanics
publication_identifier:
issn:
- '00221120'
publication_status: published
publisher: Cambridge University Press
publist_id: '6922'
quality_controlled: '1'
scopus_import: '1'
status: public
title: Transition to turbulence in pulsating pipe flow
type: journal_article
user_id: c635000d-4b10-11ee-a964-aac5a93f6ac1
volume: 831
year: '2017'
...
---
_id: '1339'
abstract:
- lang: eng
text: "We present a microelectromechanical system, in which a silicon beam is attached
to a comb-drive\r\nactuator, which is used to tune the tension in the silicon
beam and thus its resonance frequency. By\r\nmeasuring the resonance frequencies
of the system, we show that the comb-drive actuator and the\r\nsilicon beam behave
as two strongly coupled resonators. Interestingly, the effective coupling rate\r\n(1.5
MHz) is tunable with the comb-drive actuator (10%) as well as with a side-gate
(10%)\r\nplaced close to the silicon beam. In contrast, the effective spring constant
of the system is insensitive\r\nto either of them and changes only by 60.5%. Finally,
we show that the comb-drive actuator\r\ncan be used to switch between different
coupling rates with a frequency of at least 10 kHz.\r\n"
acknowledgement: We acknowledge the support from the Helmholtz Nanoelectronic Facility
(HNF) and funding from the ERC (GA-Nr. 280140).
article_number: '143507'
author:
- first_name: Gerard
full_name: Verbiest, Gerard
last_name: Verbiest
- first_name: Duo
full_name: Xu, Duo
id: 3454D55E-F248-11E8-B48F-1D18A9856A87
last_name: Xu
- first_name: Matthias
full_name: Goldsche, Matthias
last_name: Goldsche
- first_name: Timofiy
full_name: Khodkov, Timofiy
last_name: Khodkov
- first_name: Shabir
full_name: Barzanjeh, Shabir
id: 2D25E1F6-F248-11E8-B48F-1D18A9856A87
last_name: Barzanjeh
orcid: 0000-0003-0415-1423
- first_name: Nils
full_name: Von Den Driesch, Nils
last_name: Von Den Driesch
- first_name: Dan
full_name: Buca, Dan
last_name: Buca
- first_name: Christoph
full_name: Stampfer, Christoph
last_name: Stampfer
citation:
ama: Verbiest G, Xu D, Goldsche M, et al. Tunable mechanical coupling between driven
microelectromechanical resonators. Applied Physics Letter. 2016;109. doi:10.1063/1.4964122
apa: Verbiest, G., Xu, D., Goldsche, M., Khodkov, T., Barzanjeh, S., Von Den Driesch,
N., … Stampfer, C. (2016). Tunable mechanical coupling between driven microelectromechanical
resonators. Applied Physics Letter. American Institute of Physics. https://doi.org/10.1063/1.4964122
chicago: Verbiest, Gerard, Duo Xu, Matthias Goldsche, Timofiy Khodkov, Shabir Barzanjeh,
Nils Von Den Driesch, Dan Buca, and Christoph Stampfer. “Tunable Mechanical Coupling
between Driven Microelectromechanical Resonators.” Applied Physics Letter.
American Institute of Physics, 2016. https://doi.org/10.1063/1.4964122.
ieee: G. Verbiest et al., “Tunable mechanical coupling between driven microelectromechanical
resonators,” Applied Physics Letter, vol. 109. American Institute of Physics,
2016.
ista: Verbiest G, Xu D, Goldsche M, Khodkov T, Barzanjeh S, Von Den Driesch N, Buca
D, Stampfer C. 2016. Tunable mechanical coupling between driven microelectromechanical
resonators. Applied Physics Letter. 109, 143507.
mla: Verbiest, Gerard, et al. “Tunable Mechanical Coupling between Driven Microelectromechanical
Resonators.” Applied Physics Letter, vol. 109, 143507, American Institute
of Physics, 2016, doi:10.1063/1.4964122.
short: G. Verbiest, D. Xu, M. Goldsche, T. Khodkov, S. Barzanjeh, N. Von Den Driesch,
D. Buca, C. Stampfer, Applied Physics Letter 109 (2016).
date_created: 2018-12-11T11:51:28Z
date_published: 2016-10-04T00:00:00Z
date_updated: 2023-02-21T10:35:06Z
day: '04'
department:
- _id: JoFi
doi: 10.1063/1.4964122
intvolume: ' 109'
language:
- iso: eng
main_file_link:
- open_access: '1'
url: https://arxiv.org/abs/1607.04406
month: '10'
oa: 1
oa_version: Preprint
publication: Applied Physics Letter
publication_status: published
publisher: American Institute of Physics
publist_id: '5928'
quality_controlled: '1'
scopus_import: 1
status: public
title: Tunable mechanical coupling between driven microelectromechanical resonators
type: journal_article
user_id: 3E5EF7F0-F248-11E8-B48F-1D18A9856A87
volume: 109
year: '2016'
...