Leijian Song

Shanghai Electric (China)

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Shixiao Fu

Shanghai Jiao Tong University

Mengmeng Zhang

Shanghai Cancer Institute

Haojie Ren

Inner Mongolia University

Yun Gao

Xi'an Jiaotong University

Tie Ren

Shanghai Jiao Tong University

Ziqi Lu

Massachusetts Institute of Technology

Leixin Ma

University of California, Los Angeles

Shixiao Fu

Shanghai Jiao Tong University

Halvor Lie

SINTEF

Yifan Chen

University of Electronic Science and Technology of China

Cooperative Institutions

Shanghai Jiao Tong University

Shanghai Ocean University

Collaborative Innovation Centre for Advanced Ship and Deep-Sea Exploration

State Key Laboratory of Ocean Engineering

Chinese Academy of Medical Sciences & Peking Union Medical College

Massachusetts Institute of Technology

Chinese Academy of Sciences

Northwestern Polytechnical University

SINTEF

Nanyang Technological University

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Hydrodynamics of Flexible Pipe With Staggered Buoyancy Elements Undergoing Vortex-Induced Vibrations

Journal of Offshore Mechanics and Arctic Engineering (2018)

Mengmeng Zhang Shixiao Fu Leijian Song Jie Wu Halvor Lie

Flexible pipe with staggered buoyancy elements such as lazy wave riser and drilling riser has been widely used in ocean engineering. Under the influence of sea current, both of the buoyancy elements and the riser may experience vortex induced vibrations (VIV). However, when VIV occurs, hydrodynamic characteristics of the buoyancy elements and its influence on hydrodynamic force of the bare pipe still need investigation. The purpose of this paper is to reveal the hydrodynamic characteristics of flexible pipe with staggered buoyancy elements undergoing VIV. The crossflow (CF) hydrodynamic coefficients of the flexible pipe with 25%, 50%, and 100% coverage of staggered buoyancy are obtained from model tests, using hydrodynamic forces and coefficients identification method. Then, the characteristics of added mass coefficients and excitation coefficients in CF direction are analyzed. The results show that the added-mass coefficients of bare pipe are relatively larger than those of buoyancy module, while the total mass per unit length (sum of structural mass and added mass) is consistent along the pipe. Similarly, the range of excitation coefficient on the buoyancy elements is smaller than that on the bare pipe, and their ratio is equal to the reciprocal of diameter ratio 2.5.

Added mass

Drilling riser

10.1115/1.4040509

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Citations (14)

VIV response of a long flexible riser fitted with strakes in uniform and linearly sheared currents

Applied Ocean Research (2015)

Yun Gao Shixiao Fu Tie Ren Youming Xiong Leijian Song

Towing

Drilling riser

Vortex-induced vibration

10.1016/j.apor.2015.05.006

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Citations (83)

Experimental Investigation on the Suppression Device of VIV of a Flexible Riser

Yun Gao Shixiao Fu Leijian Song Peng Tao Runpei Lei

Experimental investigations were conducted on a flexible riser with and without helical strakes. A uniform current was obtained by towing a riser model in a tank, and the vortex-induced vibration (VIV) suppression of strakes with different heights and pitches was studied. The results of the bare riser show that the characteristics of the synchronization of the VIV for a flexible riser have many orders, and the excited mode jumps from one to another abruptly. During the high order synchronization regime, the VIV response decreases with the increased order of the synchronization. The experimental results also indicate that the response characteristics of a bare riser can be quite distinct from those of a riser with helical strakes, and the suppression performance depends on the geometry of the helical strakes. The fatigue damage in the CF direction is of the same order as that in the IL direction for the bare riser. However, for the riser fitted with helical strakes, the fatigue damage in the CF direction is much smaller than that in the IL direction. The experimental results also confirmed that strake height has a greater influence on the VIV response than the strake pitch, and the drag exerted on the riser increases with strake pitch and height.

Towing

Drilling riser

Vortex-induced vibration

10.1115/omae2014-23427

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Citations (5)

Distribution of drag force coefficient along a flexible riser undergoing VIV in sheared flow

Ocean Engineering (2016)

Leijian Song Shixiao Fu Siyu Dai Mengmeng Zhang Yifan Chen

Zero-lift drag coefficient

Drag equation

Vortex-induced vibration

10.1016/j.oceaneng.2016.08.022

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Citations (30)

Hydrodynamics of A Flexible Riser Undergoing the Vortex-Induced Vibration at High Reynolds Number

China Ocean Engineering (2018)

Tie Ren Mengmeng Zhang Shixiao Fu Leijian Song

This study proposed a method to obtain hydrodynamic forces and coefficients for a flexible riser undergoing the vortex-induced vibration (VIV), based on the measured strains collected from the scale-model testing with the Reynolds numbers ranging from 1.34E5 to 2.35E5. The riser is approximated as a tensioned spatial beam, and an inverse method based on the FEM of spatial beam is adopted for the calculation of hydrodynamic forces in the cross flow (CF) and inline (IL) directions. The drag coefficients and vortex-induced force coefficients are obtained through the Fourier Series Theory. Finally, the hydrodynamic characteristics of a flexible riser model undergoing the VIV in a uniform flow are carefully investigated. The results indicate that the VIV amplifies the drag coefficient, and the drag coefficient does not change with time when the CF VIV is stable. Only when the VIVs in the CF and IL directions are all steady vibrations, the vortex-induced force coefficients keep as a constant with time, and under "lock-in" condition, whether the added-mass coefficient changes with time or not, the oscillation frequency of the VIV keeps unchanged. It further shows that the CF excitation coefficients at high frequency are much smaller than those at the dominant frequency, while, the IL excitation coefficients are in the same range. The axial distributions of the excitation and damping region at the dominant frequency and high frequency are approximately consistent in the CF direction, while, in the IL direction, there exists a great difference.

Vortex-induced vibration

Oscillation (cell signaling)

Added mass

Morison equation

Vortex shedding

10.1007/s13344-018-0059-0

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Citations (5)

A time domain prediction method for the vortex-induced vibrations of a flexible riser

Marine Structures (2018)

Mengmeng Zhang Shixiao Fu Leijian Song Xiaoying Tang Yue He

Vortex-induced vibration

Tension (geology)

Added mass

Morison equation

10.1016/j.marstruc.2018.02.010

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Citations (33)

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

Journal of Offshore Mechanics and Arctic Engineering (2017)

Leijian Song Shixiao Fu Tie Ren Ziqi Lu

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.

Vortex-induced vibration

Vortex shedding

10.1115/1.4035768

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Citations (3)

Stress analysis model for un-bonded umbilical cables

Ocean Systems Engineering (2013)

Xiqia Chen Shixiao Fu Leijian Song Qian Zhong Xiaoping Huang

For the optimization design and strength evaluation of the umbilical cable, the calculation of cross section stress is of great importance and very time consuming. To calculate the cross section stress under combined tension and bending loads, a new integrated analytical model of umbilical cable is presented in this paper. Based on the Hook's law, the axial strain of helical components serves as the tensile stress. Considering the effects of friction between helical components, the bending stress is divided into elastic bending stress and friction stress. For the former, the elastic bending stress, the curvature of helical components is deduced; and for the latter, the shear stress before and after the slipping of helical components is determined. This new analytical model is validated by the experimental results of an umbilical cable. Further, this model is applied to estimate the extreme strength and fatigue life of the umbilical cable used in South China Sea.

Slipping

Tension (geology)

Stress–strain curve

10.12989/ose.2013.3.2.097

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Citations (3)

Characterization of wake interference between two tandem offshore floating vertical-axis wind turbines: Effect of platform pitch motion

Energy Conversion and Management (2022)

Limin Kuang Lu Qi Xuan Huang Leijian Song Yaoran Chen

10.1016/j.enconman.2022.115769

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Citations (26)

Nonlinear Hydrodynamics of a Floating Cylinder in Oscillatory Flow Alone and Combined with a Current

Journal of Waterway Port Coastal and Ocean Engineering (2016)

Ke Hu Shixiao Fu Leixin Ma Leijian Song

This paper experimentally investigates the nonlinear hydrodynamic forces on a semisubmerged floating collar under full-scale Reynolds number (R) and Keulegan-Carpenter number (KC) oscillatory flow alone and combined with a current. The collar was forced to oscillate harmonically in the direction of the current within a wide range of oscillation amplitudes and frequencies. The first five orders of the horizontal hydrodynamic forces are obtained using Fourier transformation techniques. The influence of the KC, the frequency parameter (β), and the reduced velocity (Vr) on the high-order components of the hydrodynamic force were investigated. The results show that, under oscillatory flows, the first five harmonics of the hydrodynamic force coefficients increase with an increase of KC and β. As the reduced velocity (Vr) increases, the first- and second-order components are greatly affected. These first two order components contribute greatly to the overall hydrodynamic force in the combined flow condition, with no apparent slamming, whereas the last three orders contribute less. The first two harmonics agree well with the experimental results when overtopping occurs; however, differences are apparent where slamming occurs.

Slamming

Oscillation (cell signaling)

Kármán vortex street

10.1061/(asce)ww.1943-5460.0000359

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Citations (4)