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A Review on Vibration Control of Multiple Cylinders Subjected to FlowInduced Vibrations

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China Ocean Engineering 2024年第2期38卷 183-197页

作者： xu wan-hai MA Ye-xuan State Key Laboratory of Hydraulic Engineering Intelligent Construction and Operation Tianjin UniversityTianjin 300350China Institute of Mechanics Chinese Academy of SciencesBeijing 100190China

The fatigue damage caused by flow-induced vibration(FIV)is one of the major concerns for multiple cylindrical structures in many engineering *** FIV suppression is of great importance for the security of many cylindrical *** active and passive control methods have been employed for the vibration suppression of an isolated cylinder undergoing vortex-induced vibrations(VIV).The FIV suppression methods are mainly extended to the multiple cylinders from the vibration control of the isolated *** to the mutual interference between the multiple cylinders,the FIV mechanism is more complex than the VIV mechanism,which makes a great challenge for the FIV *** efforts have been devoted to vibration suppression of multiple cylinder systems undergoing FIV over the past two *** control methods,such as helical strakes,splitter plates,control rods and flexible sheets,are not always effective,depending on many influence factors,such as the spacing ratio,the arrangement geometrical shape,the flow velocity and the parameters of the vibration control *** FIV response,hydrodynamic features and wake patterns of the multiple cylinders equipped with vibration control devices are reviewed and *** FIV suppression efficiency of the vibration control methods are analyzed and compared considering different influence *** research on the FIV suppression of multiple cylinders is suggested to provide insight for the development of FIV control methods and promote engineering applications of FIV control methods.

关键词： flow-induced vibration vibration control multiple cylinders tandem side-by-side staggered

Vortex-Induced Vibrations of A Free-Spanning Pipe Based on A Nonlinear Hysteretic Soil Model at the Shoulders

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China Ocean Engineering 2020年第3期34卷 328-340页

作者： GAO Xi-feng XIE Wu-de xu wan-hai State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

The pipe-soil interactions at shoulders can significantly affect the vortex-induced vibrations (VIV) of free-spanning pipes in the subsea. In this paper, the seabed soil reacting force on the pipe is directly calculated with a nonlinear hysteretic soil model. For the VIV in the middle span, a classic van der Pol wake oscillator is adopted. Based on the Euler-Bernoulli beam theory, the vibration equations of the pipe are obtained which are different in the middle span and at the two end shoulders. The static configuration of the pipe is firstly calculated and then the VIV is *** present model is validated with the comparisons of VIV experiment, pipe-soil interaction experiment and the simulation results of VIV of free-spanning pipes in which the seabed soil is modelled with spring-dashpots. With the present model, the influence of seabed soil on the VIV of a free-spanning pipe is analyzed. The parametric studies show that when the seabed soil has a larger suction area, the pipe vibrates with smaller bending stresses and is *** with the increase of the shear strength of the seabed soil, the bending stresses increase and the pipe faces more danger.

关键词： free-spanning pipe vortex-induced vibrations nonlinear hysteretic soil model bending stresses

Use of Helical Strakes for FIV Suppression of Two Inclined Flexible Cylinders in A Side-by-Side Arrangement

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China Ocean Engineering 2018年第3期32卷 331-340页

作者： xu wan-hai ZHANG Shu-hai ZHOU Li-dan GAO Xi-feng State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Collaborative Innovation Centre for Advanced Ship and Deep-Sea Exploration Shanghai 200240China

The experimental studies on flow-induced vibrations(FIV) reduction of two side-by-side flexible cylinders inclined at 45° by using the helical strakes were carried out in a towing tank. The main aim of the experiment is to check whether the helical strakes with a pitch of 17.5 D and a height of 0.25 D, which is considered as the most effective vibration suppression device for the isolated cylinder undergoing vortex-shedding, still perform very well to reduce FIV of two inclined flexible cylinders in a side-by-side arrangement. The vibration of two identical inclined cylinders with a mass ratio of 1.90 and an aspect ratio of 350 was tested in the experiment. The center-to-center distance between the two cylinders was 3.0 D. The uniform flow was simulated by towing the cylinder models along the *** towing velocity varied from 0.05 to 1.0 m/s with an interval of 0.05 m/s. The maximum Reynolds number can be up to 1.6×104. Three cases were experimentally studied in this paper, including two side-by-side inclined smooth cylinders, only one smooth cylinder fitted with helical strakes in the two side-by-side inclined cylinders system and both two cylinders attached with helical strakes. The variations of displacement amplitude, dominant frequency, FIV suppression efficiency and dominant mode for the two side-by-side inclined cylinders with reduced velocity were shown and discussed.

关键词： helical strakes FIV suppression inclined cylinder side-by-side towing tank experiment

Flow-Induced Vibration Fatigue Damage of A Pair of Flexible Cylinders in A Staggered Array

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China Ocean Engineering 2021年第6期35卷 878-890页

作者： xu wan-hai LI Yu-han JIA Kun LAI Jiang State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Nuclear Power Institute of China Chengdu 610041China

Flow-induced vibration(FIV)of a group of long,flexible cylinders involves a complex interaction between fluid and *** a substantial number of studies have been devoted to assessing FIV response behaviours,fatigue damage features of staggered flexible cylinders are not fully ***,the wake-induced flutter constitutes an intricate hydrodynamic behaviour that frequently occurs when one cylinder is in the vicinity of another ***,existing studies on the fatigue damage caused by wake-induced flutter are incapable of achieving better *** paper,therefore,estimates the FIV fatigue damage of two staggered flexible cylinders with an aspect ratio of 350 and a mass ratio of 1.90 based on normal S−N curves according to Det Norske Veritas(DNV)*** staggered cases(cross-flow spacing ratios of 2.0,3.0,4.0,and 6.0 and in-line spacing ratios of 4.0,6.0,and 8.0)are discussed for comparison,and fatigue damage caused by wake-induced flutter is thoroughly *** damage results indicate that the variation of the cross-flow(CF)spacing ratio has a greater influence than that of the in-line(IL)spacing ratio on the CF fatigue damage of the upstream *** IL fatigue damages of the upstream cylinder are observed when reduced velocity V_(r)≥15.03 due to the wake flow patterns with different IL spacing ***,wake interference,especially wake-induced flutter,predominates the fatigue damage characteristics of the downstream *** V_(r)=8.77−11.27,wake-induced flutter enhances the IL fatigue damage of the downstream cylinder and slightly affects that of the upstream ***,wake-induced flutter causes considerable IL fatigue damage disparity between the two staggered cylinders by suppressing the IL fatigue damage of the upstream cylinder when V_(r)≥20.04.

关键词： flow-induced vibration fatigue damage flexible cylinder staggered arrangement wake-induced flutter

Study on Pure IL VIV of A Free Spanning Pipeline Under General Boundary Conditions

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China Ocean Engineering 2017年第1期31卷 114-122页

作者： xu wan-hai xu Jing-yu WU Ying-xiang JI Chun-ning State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University Tianjin 300072 China Collabomtive Innovation Centre for Advanced Ship and Deep-Sea Exploration Shanghai 200240 China Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

Pipeline spans may occur due to natural seabed irregularities or local scour of bed sediment. The pure in-line（IL）vortex-induced vibrations（VIV） analysis of the free spans is an important subject for design of pipeline in uneven seabed. The main objective of this paper is to analyze the characteristics of pure IL VIV of a free spanning pipeline under general boundary conditions. An IL wake oscillator model which can describe the coupling of pipeline structure and fluctuating drag is introduced and employed. The coupled partial differential equations of structure and wake are transformed into a set of ordinary differential equations using two-mode Galerkin method. Some case studies are presented and thoroughly discussed in order to investigate the effects of internal fluid, axial force and boundary conditions on the pure IL VIV.

关键词： pipeline oscillator spans Pipeline spanning transformed fluctuating details offshore ordinary

Vortex-Induced Vibration Response Features of A Submarine Multi-Span Pipeline via Towing Tank Experimental Tests

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China Ocean Engineering 2023年第2期37卷 175-189页

作者： xu wan-hai JIA Kun MA Ye-xuan SONG Zhi-you State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China

In offshore engineering, the phenomenon of free span often occurs, and the pipeline may have multiple free spans adjacent to each other, forming a multi-span pipeline. The interaction of different spans makes the structural vibration characteristics more complex, which may change the fatigue characteristics of the pipeline and affect the safety of the structure. In this paper, model tests were designed to explore the vortex-induced vibration(VIV) characteristics of multi-span pipelines and investigate the multi-span interaction mechanism. The experimental study mainly focused on the dynamic response of double-span pipelines, and further extended to triple-span pipelines, hoping that the results can be applied to more complex environment. The effects of span-length ratio, buried depth and axial force on VIV of the pipeline were investigated and discussed. The dynamic response of the pipeline varied with the span length. There was obvious interaction between different spans of multi-span pipelines, and the pipe-sediment interaction obviously affected the vibration characteristics of pipeline. The differences of pipeline burial depth and axial force changed the structural stiffness. With the increase of buried depth, the response amplitude presented a downward trend. The spanwise evolutions were asymmetric caused by the pipe-sediment interaction and multi-span interaction. The results can help to identify multi-span pipelines in engineering, and realize the prevention and control of free spans.

关键词： vortex-induced vibration submarine pipeline pipe-sediment interaction multi-span interaction

Passive VIV Reduction of An Inclined Flexible Cylinder by Means of Helical Strakes with Round-Section

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China Ocean Engineering 2018年第4期32卷 413-421页

作者： xu wan-hai QIN Wen-qi HE Ming GAO Xi-feng State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University

A series of experimental tests of passive VIV suppression of an inclined flexible cylinder with round-sectioned helical strakes were carried out in a towing tank. During the tests, the cylinder models fitted with and without helical strakes were towed along the tank. The towing velocity ranged from 0.05 to 1.0 m/s with an interval of 0.05 m/*** different yaw angles(a=0°, 15°, 30° and 45°), defined as the angle between the axis of the cylinder and the plane orthogonal of the oncoming flow, were selected in the experiment. The main purpose of present experimental work is to further investigate the VIV suppression effectiveness of round-sectioned helical strakes on the inclined flexible cylinder. The VIV responses of the smooth cylinder and the cylinder with square-sectioned strakes under the same experimental condition were also presented for comparison. The experimental results indicated that the roundsectioned strake basically had a similar effect on VIV suppression compared with the square-sectioned one, and both can significantly reduce the VIV of the vertical cylinder which corresponded to the case of a=0°. But with the increase of yaw angle, the VIV suppression effectiveness of both round-and square-section strakes deteriorated dramatically, the staked cylinder even had a much stronger vibration than the smooth one did in the in-line(IL)direction.

关键词： VIV suppression Helical strakes inclined flexible cylinder yaw angle round-section

Response of Two Unequal-Diameter Flexible Cylinders in A Side-by-Side Arrangement:Characteristics of FIV

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China Ocean Engineering 2020年第4期34卷 475-487页

作者： xu wan-hai ZHANG Qian-nan MA Wen-chen wanG En-hao State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China Department of Civil and Environmental Engineering and Construction University of NevadaNV 89154USA

Till now,little information is available on the flow-induced vibration(FIV)of multiple flexible cylinders with unequal *** FIV characteristics of unequal-diameter cylinders can be predicted based on the knowledge of equal-diameter cylinders,while there are still other features remaining *** this paper,the FIV characteristics of two flexible cylinders with unequal diameters arranged side-by-side are experimentally *** diameter ratio of the small cylinder(Small Cyl.)to the large cylinder(Large Cyl.)is nearly *** aspect ratios and mass ratios of the two flexible cylinders are 350/181 and 1.90/1.47,*** centre-tocentre spacing ratio in the cross-flow(CF)direction is kept constant as 6.0 and the two cylinders can oscillate freely in both the CF and in-line(IL)*** towing velocity varies from 0.05 m/s to 1.00 m/*** dominant modes and frequencies,CF and IL displacement amplitudes and response trajectories are *** with the case of two identical cylinders in our previous study,the FIV responses demonstrate some similarities and *** similarities are as *** cylinders exhibit multi-mode vibration features and they interact with each ***,the IL FIV shows a more complex behaviour than that in the CF *** difference is that as the diameter of one cylinder is increased,the effect on the smaller cylinder becomes more *** Large Cyl.,the FIV response is similar to its isolated counterpart,which indicates that Small *** a negligible effect on the FIV of the larger *** Large *** the FIV of Small *** the vibration *** spacing would change when both cylinders are *** interference between the two cylinders and wake shielding effect of the Large *** *** dominant frequencies of Small *** reduced and the wake-induced flutter of Small *** observed from the response trajectories at different mea

关键词： flow-induced vibration(FIV) flexible cylinder side-by-side unequal diameter wake-induced flutter

Passive Control of Flow-Induced Vibration(FIV)by Helical Strakes for Two Staggered Flexible Cylinders

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China Ocean Engineering 2021年第4期35卷 475-489页

作者： xu wan-hai wanG Qi-cheng QIN Wen-qi DU Zun-feng State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin UniversityTianjin 300072China School of Civil Engineering Tianjin UniversityTianjin 300072China CIMC Offshore Co.Ltd Shenzhen 518000China

Helical strake is a widely-used device for passive flow-induced vibration(FIV)control of cylindrical *** is omnidirectional and can effectively reduce FIV response *** on the passive FIV control for cylindrical structures are mainly concerned with a single isolated cylinder,while the influence of wake interference between multiple cylinders on FIV suppression devices is less considered up to *** engineering applications,multiple flexible cylinders with large aspect ratios can be subjected to complex flow forces,and the effects of wake interference are *** FIV suppression effect of helical strake of a common configuration(17.5D pitch and 0.25D height,where D is the cylinder diameter)in two staggered cylinders system is still *** paper systematically studied the FIV response of multiple cylinders system fitted with the helical strakes by model *** relative spatial position of the two cylinders is fixed at S=3.0D and T=8.0D,which ensures the cylindrical structures in the flow interference *** experimental results show that the helical strakes effectively reduce the FIV response on staggered upstream cylinder,and the suppression efficiency is barely affected by the smooth or straked downstream *** corresponding FIV suppression efficiency on the downstream cylinder is remarkably reduced by the influence of the upstream wake *** wake-induced vibration(WIV)phenomenon is not observed on the staggered downstream cylinder,which normally occurs on the downstream straked cylinder in a tandem arrangement.

关键词： flow-induced vibration(FIV) passive control helical strakes flexible cylinders staggered arrangement