Simultaneous measurement of the distributed longitudinal strain and velocity field for a cantilevered cylinder exposed to turbulent cross flow
File(s)s00348-024-03870-5.pdf (1.97 MB)
Published version
Author(s)
Oliveira, Francisco
Sharif Khodaei, Zahra
Buxton, Oliver
Type
Journal Article
Abstract
The structural response of a cantilevered cylinder under free-stream conditions both with low and
high turbulence intensity (TI) generated by turbulence-generating grids is analysed with concurrent
measurements of the velocity field and the distributed strain. The thin-walled cylinder, with a diameter
(D) of 50 mm, is mounted in a water flume as a cantilevered beam supported at one end, with 95%
of its body submerged and exposed to crossflow yielding a Reynolds number of Re = 25000. We
employ a novel combination of simultaneous particle image velocimetry (PIV) and distributed strain
measurements using Rayleigh backscattering fiber optic sensors (RBS). These sensors are embedded
onto the surface of the cylinder to measure the experienced strain (ε) of the structure along its
spanwise direction, covering both the windward and leeward faces of the cylinder. The sensors fine
spatial resolution allows us to discern the influence of the flow on the structural response of the cylinder
in two distinct regions of the structure: upstream and downstream of the mean separation location.
This differentiation allows us to isolate the local effects introduced by the free-stream conditions on
the loading events over the body from the global force generated by the vortex shedding and other
coherent motions present within the flow. Distinguishing between these direct and indirect effects
helps determine which is more relevant for fatigue-life cycle analysis. The cross power spectral density
between the fluctuating velocity field and the strain reveals that the load is dominated by the vortex
shedding, and this relationship is intensified with the introduction of free-stream turbulence. It also
helps to discern the different dynamics imposed by the two free-stream turbulence conditions.
high turbulence intensity (TI) generated by turbulence-generating grids is analysed with concurrent
measurements of the velocity field and the distributed strain. The thin-walled cylinder, with a diameter
(D) of 50 mm, is mounted in a water flume as a cantilevered beam supported at one end, with 95%
of its body submerged and exposed to crossflow yielding a Reynolds number of Re = 25000. We
employ a novel combination of simultaneous particle image velocimetry (PIV) and distributed strain
measurements using Rayleigh backscattering fiber optic sensors (RBS). These sensors are embedded
onto the surface of the cylinder to measure the experienced strain (ε) of the structure along its
spanwise direction, covering both the windward and leeward faces of the cylinder. The sensors fine
spatial resolution allows us to discern the influence of the flow on the structural response of the cylinder
in two distinct regions of the structure: upstream and downstream of the mean separation location.
This differentiation allows us to isolate the local effects introduced by the free-stream conditions on
the loading events over the body from the global force generated by the vortex shedding and other
coherent motions present within the flow. Distinguishing between these direct and indirect effects
helps determine which is more relevant for fatigue-life cycle analysis. The cross power spectral density
between the fluctuating velocity field and the strain reveals that the load is dominated by the vortex
shedding, and this relationship is intensified with the introduction of free-stream turbulence. It also
helps to discern the different dynamics imposed by the two free-stream turbulence conditions.
Date Issued
2024-09
Date Acceptance
2024-08-11
Citation
Experiments in Fluids: experimental methods and their applications to fluid flow, 2024, 65 (9), pp.1-12
ISSN
0723-4864
Publisher
Springer
Start Page
1
End Page
12
Journal / Book Title
Experiments in Fluids: experimental methods and their applications to fluid flow
Volume
65
Issue
9
Copyright Statement
© The Author(s) 2024 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
License URL
Identifier
https://link.springer.com/article/10.1007/s00348-024-03870-5
Publication Status
Published
Article Number
134
Date Publish Online
2024-08-31