---
_id: '2050'
abstract:
- lang: eng
  text: The flow instability and further transition to turbulence in a toroidal pipe
    (torus) with curvature ratio (tube-to-coiling diameter) 0.049 is investigated
    experimentally. The flow inside the toroidal pipe is driven by a steel sphere
    fitted to the inner pipe diameter. The sphere is moved with constant azimuthal
    velocity from outside the torus by a moving magnet. The experiment is designed
    to investigate curved pipe flow by optical measurement techniques. Using stereoscopic
    particle image velocimetry, laser Doppler velocimetry and pressure drop measurements,
    the flow is measured for Reynolds numbers ranging from 1000 to 15 000. Time- and
    space-resolved velocity fields are obtained and analysed. The steady axisymmetric
    basic flow is strongly influenced by centrifugal effects. On an increase of the
    Reynolds number we find a sequence of bifurcations. For Re=4075±2% a supercritical
    bifurcation to an oscillatory flow is found in which waves travel in the streamwise
    direction with a phase velocity slightly faster than the mean flow. The oscillatory
    flow is superseded by a presumably quasi-periodic flow at a further increase of
    the Reynolds number before turbulence sets in. The results are found to be compatible,
    in general, with earlier experimental and numerical investigations on transition
    to turbulence in helical and curved pipes. However, important aspects of the bifurcation
    scenario differ considerably.
article_processing_charge: No
arxiv: 1
author:
- first_name: Jakob
  full_name: Kühnen, Jakob
  id: 3A47AE32-F248-11E8-B48F-1D18A9856A87
  last_name: Kühnen
  orcid: 0000-0003-4312-0179
- first_name: Markus
  full_name: Holzner, Markus
  last_name: Holzner
- first_name: Björn
  full_name: Hof, Björn
  id: 3A374330-F248-11E8-B48F-1D18A9856A87
  last_name: Hof
  orcid: 0000-0003-2057-2754
- first_name: Hendrik
  full_name: Kuhlmann, Hendrik
  last_name: Kuhlmann
citation:
  ama: Kühnen J, Holzner M, Hof B, Kuhlmann H. Experimental investigation of transitional
    flow in a toroidal pipe. <i>Journal of Fluid Mechanics</i>. 2014;738:463-491.
    doi:<a href="https://doi.org/10.1017/jfm.2013.603">10.1017/jfm.2013.603</a>
  apa: Kühnen, J., Holzner, M., Hof, B., &#38; Kuhlmann, H. (2014). Experimental investigation
    of transitional flow in a toroidal pipe. <i>Journal of Fluid Mechanics</i>. Cambridge
    University Press. <a href="https://doi.org/10.1017/jfm.2013.603">https://doi.org/10.1017/jfm.2013.603</a>
  chicago: Kühnen, Jakob, Markus Holzner, Björn Hof, and Hendrik Kuhlmann. “Experimental
    Investigation of Transitional Flow in a Toroidal Pipe.” <i>Journal of Fluid Mechanics</i>.
    Cambridge University Press, 2014. <a href="https://doi.org/10.1017/jfm.2013.603">https://doi.org/10.1017/jfm.2013.603</a>.
  ieee: J. Kühnen, M. Holzner, B. Hof, and H. Kuhlmann, “Experimental investigation
    of transitional flow in a toroidal pipe,” <i>Journal of Fluid Mechanics</i>, vol.
    738. Cambridge University Press, pp. 463–491, 2014.
  ista: Kühnen J, Holzner M, Hof B, Kuhlmann H. 2014. Experimental investigation of
    transitional flow in a toroidal pipe. Journal of Fluid Mechanics. 738, 463–491.
  mla: Kühnen, Jakob, et al. “Experimental Investigation of Transitional Flow in a
    Toroidal Pipe.” <i>Journal of Fluid Mechanics</i>, vol. 738, Cambridge University
    Press, 2014, pp. 463–91, doi:<a href="https://doi.org/10.1017/jfm.2013.603">10.1017/jfm.2013.603</a>.
  short: J. Kühnen, M. Holzner, B. Hof, H. Kuhlmann, Journal of Fluid Mechanics 738
    (2014) 463–491.
corr_author: '1'
date_created: 2018-12-11T11:55:25Z
date_published: 2014-01-10T00:00:00Z
date_updated: 2025-09-29T11:51:23Z
day: '10'
department:
- _id: BjHo
doi: 10.1017/jfm.2013.603
external_id:
  arxiv:
  - '1508.06546'
  isi:
  - '000328486400021'
intvolume: '       738'
isi: 1
language:
- iso: eng
main_file_link:
- open_access: '1'
  url: https://arxiv.org/abs/1508.06546
month: '01'
oa: 1
oa_version: Submitted Version
page: 463 - 491
publication: Journal of Fluid Mechanics
publication_status: published
publisher: Cambridge University Press
publist_id: '5001'
quality_controlled: '1'
scopus_import: '1'
status: public
title: Experimental investigation of transitional flow in a toroidal pipe
type: journal_article
user_id: 317138e5-6ab7-11ef-aa6d-ffef3953e345
volume: 738
year: '2014'
...