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Research Papers: CFD and VIV

Phase Angles of the Vibrations and Hydrodynamic Forces of the Flexible Risers Undergoing Vortex-Induced Vibration

[+] Author and Article Information
Leijian Song

State Key Laboratory of Ocean Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China;
Collaborative Innovation Centre for Advanced
Ship and Deep-Sea Exploration,
Shanghai 200240, China

Shixiao Fu

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

Tie Ren

State Key Laboratory of Ocean Engineering,
Shanghai Jiao Tong University,
Shanghai 200240, China;
Collaborative Innovation Centre for Advanced
Ship and Deep-Sea Exploration,
Shanghai 200240, China;
Marine Design & Research Institute of China,
Shanghai 200011, China

Ziqi Lu

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

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 July 2, 2015; final manuscript received December 20, 2016; published online April 5, 2017. Assoc. Editor: Wei Qiu.

J. Offshore Mech. Arct. Eng 139(3), 031803 (Apr 05, 2017) (9 pages) Paper No: OMAE-15-1061; doi: 10.1115/1.4035768 History: Received July 02, 2015; Revised December 20, 2016

This paper investigates the phase angles of the vibrations and hydrodynamic forces by the model testing of a flexible riser's vortex-induced vibration (VIV) under uniform flow. The VIV displacement of the riser is derived from the measured strains in the cross-flow (CF) and inline (IL) directions. Then, the hydrodynamic forces are obtained by the dynamic equation of an Euler–Bernoulli beam based on the results of VIV displacement. The characteristics of the phase angle of displacement and the hydrodynamic forces are analyzed. The results show that the phase angles of displacement and the hydrodynamic forces are almost identical at different cross sections of the riser under uniform flow. Moreover, within two adjacent vibration nodes in IL direction, the phase angle almost kept constant, while had a 180 deg change at the two sides of each vibration node. When the reduced velocity varies from 5.25 to 7.5, the phase angles of displacement derived from the flexible riser's VIV are 45 deg larger than those from the rigid cylinder's self-excited vibration.

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References

Figures

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Fig. 1

Tested equipment under uniform flow

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Fig. 2

Instrumentation of strain sensors on the surface of the riser model

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Fig. 3

Motion trajectory and rotation direction with typical phase angles of displacement

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Fig. 4

Time history of CF and IL VIV displacement under a certain current speed in a cycle of CF vibration

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Fig. 5

Time histories and response spectra for the CF and IL VIV strain signals at Z/L = 0.5 (Vr = 5.68)

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Fig. 6

Time histories and response spectra for the CF and IL VIV strain signals at Z/L = 0.5 (Vr = 5.38)

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Fig. 7

Contour plot of the riser model's CF and IL VIV strains at the dominant frequency (Vr = 5.68)

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Fig. 8

Contour plot of the riser model's CF and IL VIV strains at the dominant frequency (Vr = 5.38)

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Fig. 9

The distribution of the CF and IL dominant frequencies and twice the CF dominant frequency at various reduced velocities

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Fig. 10

Time histories of the VIV displacement and hydrodynamic forces at the dominant frequency of the riser model at Z/L = 0.5(Vr = 5.68)

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Fig. 11

Division in time histories of VIV displacement at Z/L = 0.5 (Vr = 5.68)

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Fig. 12

The development with time of the motion trajectory at 19 cross sections (Vr = 5.68)

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Fig. 13

The development with time of the hydrodynamic force trajectory at 19 cross sections (Vr = 5.68)

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Fig. 14

Axial distribution of the root-mean-square (RMS) value of the nondimensional CF and IL VIV displacement and phase angles of displacement and the hydrodynamic force for various reduced velocities

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Fig. 15

Variation in the phase angle for the flexible riser's VIV displacement and the rigid cylinder's displacement with the reduced velocity

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