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Research Papers: Piper and Riser Technology

Experimental Investigation on Vortex-Induced Vibration of a Free-Hanging Riser Under Vessel Motion and Uniform Current

[+] Author and Article Information
Jungao Wang

State Key Laboratory of Ocean Engineering;Collaborative Innovation Center for
Advanced Ship and Deep-Sea Exploration,
Shanghai Jiao Tong University,
Shanghai 200240, China;
Department of Mechanical and
Structural Engineering and Materials Science,
University of Stavanger,
Stavanger NO-4036, Norway

Shixiao Fu

State Key Laboratory of Ocean Engineering;Collaborative Innovation Center for
Advanced Ship and Deep-Sea Exploration,
Shanghai Jiao Tong University,
Shanghai 200240, China;
SINTEF Ocean,
Trondheim NO-7052, Norway
e-mails: shixiao.fu@sjtu.edu.cn,
shixiao.fu@sintef.no

Jiasong Wang

State Key Laboratory of Ocean Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China

Huajun Li

College of Engineering;Shandong Province Key Laboratory of
Ocean Engineering,
Ocean University of China,
Qingdao 266100, China

Muk Chen Ong

Department of Mechanical and
Structural Engineering and Materials Science,
University of Stavanger,
Stavanger NO-4036, Norway

1Corresponding author.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received May 2, 2016; final manuscript received March 2, 2017; published online May 23, 2017. Assoc. Editor: Lizhong Wang.

J. Offshore Mech. Arct. Eng 139(4), 041703 (May 23, 2017) (18 pages) Paper No: OMAE-16-1048; doi: 10.1115/1.4036370 History: Received May 02, 2016; Revised March 02, 2017

A model test of a free-hanging riser under vessel motion and uniform current is performed in the ocean basin at Shanghai Jiao Tong University to address four topics: (1) confirm whether vortex-induced vibration (VIV) can happen due to pure vessel motion; (2) to investigate the equivalent current velocity and Keulegan–Carpenter (KC) number effect on the VIV responses; (3) to obtain the correlations for free-hanging riser VIV under vessel motion with VIV for other compliant risers; and (4) to study the similarities and differences with VIV under uniform current. The top end of the riser is forced to oscillate or move, in order to simulate vessel motion or ocean current effects. Fiber Bragg Grating (FBG) strain sensors are used to measure the riser dynamic responses. Experimental results confirm that the free-hanging riser will experience significant out-of-plane VIV under vessel motion. Meanwhile, vessel motion-induced VIV responses in terms of response amplitude, response frequency, and cross section trajectories under different test cases are further discussed and compared to those under ocean uniform current. Most importantly, the correlation among VIV response frequency, vortex shedding pairs, and maximum KC number KCmax is revealed. The presented work is supposed to provide useful references for gaining a better understanding on VIV of a free-hanging riser and for the development of future prediction models.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

Overview of the test model riser connected to the forced motion system

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Fig. 2

Sketch for the test free-hanging riser

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Fig. 3

Displacement mode shapes

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Fig. 4

Curvature mode shapes

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Fig. 5

Comparison on the local KC number distribution along the riser for the two selected vessel motion cases

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Fig. 6

Estimated riser in-plane motion velocity distribution for the vessel motion case when KCmax = 12 and Vn_max = 0.29 m/s (row (a): top horizontal motion velocity time histories; row (b): riser space- and time-varying in-plane normal velocity distribution) (See color figure online)

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Fig. 7

Estimated riser in-plane motion velocity distribution for the vessel motion case when KCmax = 71 and Vn_max = 0.37 m/s (row (a): top horizontal motion velocity time histories; row (b): riser space- and time-varying in-plane normal velocity distribution) (See color figure online)

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Fig. 8

Space-time varying strain for the vessel motion case when KCmax = 12 and Vn_max = 0.29 m/s: (a) top motion velocity, (b) top axial tension variation, (c) measured in-plane space-time varying strain, and (d) measured out-of-plane space-time varying strain (See color figure online)

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Fig. 9

Space-time varying strain for the vessel motion case when KCmax = 71 and Vn_max = 0.37 m/s: (a) top motion velocity, (b) top axial tension variation, (c) measured in-plane space-time varying strain, and (d) measured out-of-plane space-time varying strain (See color figure online)

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Fig. 10

Space-time varying strain for the uniform current case when Vc = 0.28 m/s: (a) top motion velocity, (b) top axial tension variation, (c) measured in-plane space-time varying strain, and (d) measured out-of-plane space-time varying strain (See color figure online)

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Fig. 11

Space-time varying strain for the uniform current case when Vc = 0.36 m/s: (a) top motion velocity, (b) top axial tension variation, (c) measured in-plane space-time varying strain, and (d) measured out-of-plane space-time varying strain (See color figure online)

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Fig. 12

Response frequency and section trajectory for the vessel motion case when KCmax = 12 and Vn_max = 0.29 m/s: (a) the in-plane response frequency along the riser, (b) the out-of-plane response frequency along the riser, and (c)–(g) the section trajectory at different stations (See color figure online)

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Fig. 13

Response frequency and section trajectory for the vessel motion case when KCmax = 71 and Vn_max = 0.37 m/s: (a) the in-plane response frequency along the riser, (b) the out-of-plane response frequency along the riser, and (c)–(g) the section trajectory at different stations (See color figure online)

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Fig. 14

Response frequency and section trajectory for the uniform current case when Vc = 0.28 m/s: (a) the in-plane response frequency along the riser, (b) the out-of-plane response frequency along the riser, and (c)–(g) the section trajectory at different stations (See color figure online)

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Fig. 15

Response frequency and section trajectory for the uniform current case when Vc = 0.36 m/s: (a) the in-plane response frequency along the riser, (b) the out-of-plane response frequency along the riser, and (c)–(g) the section trajectory at different station (See color figure online)

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Fig. 16

Strain time histories and time-varying response frequency for the vessel motion case when KCmax = 12, Vn_max = 0.29 m/s: (a) top vessel motion time histories; (b) top tension time histories; (c) time-varying frequency of the top tension; (d), (g), (j), (m), (p) in-plane and out-of-plane strain time histories; (e), (h), (k), (n), (q) in-plane time-varying frequency; and (f), (i), (l), (o), (r) out-of-plane time-varying frequency (See color figure online)

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Fig. 17

Strain time histories and time-varying response frequency for the vessel motion case when KCmax = 71, Vn_max = 0.37 m/s: (a) top vessel motion time histories; (b) top tension time histories; (c) time-varying frequency of the top tension; (d), (g), (j), (m), (p) the in-plane and out-of-plane strain time histories; (e), (h), (k), (n), (q) the in-plane time-varying frequency; and (f), (i), (l), (o), (r) the out-of-plane time-varying frequency (See color figure online)

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Fig. 18

Strain time histories and time-varying response frequency for the uniform current case when Vc = 0.28 m/s: (a) top vessel motion time histories; (b) top tension time histories; (c) time-varying frequency of the top tension; (d), (g), (j), (m), (p) in-plane and out-of-plane strain time histories; (e), (h), (k), (n), (q) in-plane time-varying frequency; and (f), (i), (l), (o), (r) out-of-plane time-varying frequency (See color figure online)

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Fig. 19

Strain time histories and time-varying response frequency for the uniform current case when Vc = 0.36 m/s: (a) top vessel motion time histories; (b) top tension time histories; (c) time-varying frequency of the top tension; (d), (g), (j), (m), (p) in-plane and out-of-plane strain time histories; (e), (h), (k), (n), (q) in-plane time-varying frequency; and (f), (i), (l), (o), (r) out-of-plane time-varying frequency (See color figure online)

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Fig. 20

Summarized relationship between out-of-plane strain against maximum in-plane equivalent current velocity (row (a): maximum strain and row (b): root-mean-square (RMS) strain)

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Fig. 21

General stain amplitude-frequency spectrum for the vessel motion case when KCmax = 71 and Vn_max = 0.37 m/s

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Fig. 22

Summarized relationship between out-of-plane VIV response frequency and maximum in-plane equivalent current velocity (row (a): vessel motion cases and row (b): uniform current cases)

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Fig. 23

Summarized relationship between shedding pairs per motion period and maximum KC number

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