Study on suppressing the vortex-induced vibration of flexible riser in frequency domain

2021 ◽  
Vol 116 ◽  
pp. 102882
Author(s):  
Jixiang Song ◽  
Weimin Chen ◽  
Shuangxi Guo ◽  
Dingbang Yan
Keyword(s):  
Frequency Domain ◽  
Flexible Riser ◽  
Vortex Induced Vibration

An investigation into the hydrodynamics of a flexible riser undergoing vortex-induced vibration

2016 ◽  
Vol 63 ◽  
pp. 325-350 ◽  
Author(s):  
Leijian Song ◽  
Shixiao Fu ◽  
Jing Cao ◽  
Leixin Ma ◽  
Jianqiao Wu
Keyword(s):  
Flexible Riser ◽  
Vortex Induced Vibration

Experimental Research on Vortex-Induced Vibration of Flexible Catenary Riser Model

2018 ◽  
Author(s):  
Lin Zhao ◽  
Zhimin Tan ◽  
Yucheng Hou ◽  
Yanju Yin ◽  
Weihao Meng
Keyword(s):  
Flow Velocity ◽  
Physical Model ◽  
Natural Frequency ◽  
Model Experiment ◽  
Working Condition ◽  
Experimental Results ◽  
Flexible Riser ◽  
Vortex Induced Vibration ◽  
Wave Basin ◽  
Flexible Risers

Vortex-induced vibration (VIV) is one of the most important factors accounted for the fatigue damage of long flexible risers in deep water. In this paper, the VIV response characteristics of flexible catenary riser model with the slenderness ratio of 578 were firstly studied by means of scale physical model experiments. In the experiment, the riser model was installed on a towing carriage, which might move horizontally above a wave basin with constant speed to simulate the working condition of the riser model under uniform current. The tension sensor was used to measure the time-history variation of the top tension. The acceleration sensor was used to measure the accelerations of the riser model in cross-flow (CF) and in-line (IL) directions. And the top tension, vibration spectrum, amplitude and vibration locus of the riser were analyzed in accordance with the flexible riser model experiment, and the VIV law of the model experiment working condition was analyzed; then the hydrodynamic software Orcaflex was used to verify the finite element analysis (FEA) of the experiment. The experimental results show that the flexible catenary riser with lower mass ratio and lower bending stiffness has more complex hydrodynamic characteristics than the steel catenary riser (SCR). When the suspension angle remains the same, the top tension of the riser increases with the increase of flow velocity, and the higher the flow velocity, the faster the growth rate; the natural frequency of the riser increases with the increase of flow velocity; the VIV of the riser is the second-order vibration mode when flow velocities range from 0.2m/s to 0.4m/s. The vibration frequencies corresponding to acceleration sensors at different measuring points along the axis of the riser tend to be the same and increase with the increase of flow velocity, which results in “lock-in” near a certain natural frequency close to the vortex shedding frequency. When V = 0.2m/s, the VIV responses of some measuring points of the flexible riser present a positive “8”-shape or oblique “8”-shape vibration, when the amplitude tends to be the maximum. As the flow velocity approaches to 0.8m/s, the “8”-shape vibration disappears and the VIV vibration locus begins to become cluttered, and the variation rate of the VIV phase angle is faster than that at low speeds. The experimental results show that the physical model experimental results is well matched with that of Orcaflex numerical model. The physical model experimental results can reflect the vibration law of flexible risers under actual working conditions and can be used to predict the actual vibration law and characteristics of the VIV of flexible risers.

scholarly journals Prediction of Vortex-Induced Vibration of Flexible Riser Using an Improved Wake-Oscillator Model

2009 ◽  
Author(s):  
Wein-min Chen ◽  
Liwu Zhang ◽  
Min Li
Keyword(s):  
Analytical Model ◽  
Flow Distribution ◽  
Experimental Result ◽  
Oscillator Model ◽  
Flexible Riser ◽  
Vortex Induced Vibration ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Uniform Current ◽  
Lock In

Based on improving the wake-oscillator model, an analytical model for vortex-induced vibration (VIV) of flexible riser under non-uniform current is presented, in which the variation of added mass at lock-in and the nonlinear relationship between amplitude of response and reduced velocity are considered. By means of empirical formula combining iteration computation, the improved analytical model can be conveniently programmed into computer code with simpler and faster computation process than CFD so as to be suitable to application of practical engineering. This model is validated by comparing with experimental result and numerical simulation. Our results show that the improved model can predict VIV response and lock-in region more accurately. At last, illustrative examples are given in which the amplitude of response of flexible riser experiencing VIV under action of non-uniform current is calculated and effects of riser tension and flow distribution along span of riser are explored. It is demonstrated that with the variation of tension and flow distribution, lock-in region of mode behaves in different way, and thus the final response is a synthesis of response of locked modes.

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