scholarly journals VIV Fracture Investigation into 3D Marine Riser with a Circumferential Outside Surface Crack

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jun Liu ◽  
Zhigang Du ◽  
Xiaoqiang Guo ◽  
Liming Dai ◽  
Liang Huang ◽  
...  
Keyword(s):  
Vibration Amplitude ◽  
Lateral Displacement ◽  
Axial Stress ◽  
Assessment Model ◽  
Surface Cracks ◽  
Bending Stress ◽  
Marine Riser ◽  
Vortex Induced Vibration ◽  
Marine Risers ◽  
Failure Assessment

Vortex-induced vibration (VIV) is one of the most common dynamic mechanisms that cause damage to marine risers. Hamilton’s variational principle is used to establish a vortex-induced vibration (VIV) model of a flexible riser in which the wake oscillator model is used to simulate cross-flow (CF) and inline flow (IL) vortex-induced forces and their coupling, taking into account the effect of the top tension and internal flow in the riser. The VIV model is solved by combining the Newmark-β and Runge–Kutta methods and verified with experimental data from the literature. Combining Option 1 and Option 2 failure assessment diagrams (FADs) in the BS7910 standard, a fracture failure assessment model for a marine riser with circumferential semielliptical outside surface cracks is established. Using the VIV model and FAD failure assessment chart, the effects of riser length, inside/outside flows, and top tension on the VIV response and safety assessment of marine risers with outside surface cracks are investigated. It is shown that increasing the top tension can inhibit the lateral displacement amplitude and bending stress in a riser, but excessive top tension can increase the axial stress in the riser, which counteracts the decrease in the bending stress, so that the effect of top tension on crack safety is not significant. The increasing outside flow velocity significantly increases the lateral vibration amplitude and bending stress in the riser and reduces the crack safety. When other parameters remain unchanged, increasing riser length has no significant effect on the vibration amplitude of the lower part of the riser.

scholarly journals Bifurcation analysis of vortex-induced vibration of low-dimensional models of marine risers

2021 ◽  
Vol 106 (1) ◽  
pp. 147-167
Author(s):  
Dan Wang ◽  
Zhifeng Hao ◽  
Ekaterina Pavlovskaia ◽  
Marian Wiercigroch
Keyword(s):  
Bifurcation Analysis ◽  
Vortex Induced Vibration ◽  
Marine Risers ◽  
Dimensional Models ◽  
Low Dimensional

Experimental investigation of vortex-induced vibration of long marine risers

2005 ◽  
Vol 21 (3) ◽  
pp. 335-361 ◽  
Author(s):  
A.D. Trim ◽  
H. Braaten ◽  
H. Lie ◽  
M.A. Tognarelli
Keyword(s):  
Experimental Investigation ◽  
Vortex Induced Vibration ◽  
Marine Risers

Performance Test of Electricity Generation Utilizing Vortex Induced Vibration

2011 ◽  
Author(s):  
Ryota Iiyoshi ◽  
Masahiro Kamijyo ◽  
Shuichi Yamada ◽  
Mizuyasu Koide ◽  
Tsutomu Takahashi ◽  
...  
Keyword(s):  
Electric Power ◽  
Vibration Amplitude ◽  
Electricity Generation ◽  
Performance Test ◽  
Mechanical Energy ◽  
Water Channel ◽  
Open Surface ◽  
Velocity Range ◽  
Vortex Induced Vibration ◽  
Wide Range

The Karman vortex induced vibration (KVIV) is observed over a wide range of conditions, and has been regarded as a negative phenomenon until now since it has caused many accidents. Therefore a lot of researches have been conducted to predict and to avoid it. Recently, however, KVIV is regarded as a process to convert energy of natural flows into mechanical energy, and techniques for electricity generation utilizing it are proposed. The electric power of this method is smaller than that of wind and water turbine generations, but this method has possibility to become a smaller and more maintenance-free apparatus than rotary machines. In earlier works, we found that the trailing vortex shed periodically from a cruciform two-circular-cylinder system, and that it induces a cross flow vibration on the upstream cylinder (TVIV) over a wide velocity range, which becomes broader by replacing the downstream cylinder by a strip-plate. Because of this character, an electricity generator utilizing TVIV should be effectively applied to rivers of which velocity usually varies largely. The purpose of this work is to develop a technique to generate electricity utilizing TVIV in water flow. Experiments using a water tunnel and an open-surface water channel are conducted to know conditions of the maximum electric power and to test the performance in a river. The optimum gap-to-diameter ratio is 0.22 since the cylinder vibration amplitude is largest. The optimum resistance of the circuit is the value which makes the virtual damping due to electricity generation nearly equal to the structure damping. The performance test in the water channel shows that the open surface and the turbulence in flow have little influences on the cylinder vibration amplitude and the synchronization velocity range of KVIV. However, TVIV is not observed, maybe because of the large aspect ratio.

scholarly journals Effect of Top Tension on Vortex-Induced Vibration of Deep-Sea Risers

2020 ◽  
Vol 8 (2) ◽  
pp. 121
Author(s):  
Jie Zhang ◽  
He Guo ◽  
Yougang Tang ◽  
Yulong Li
Keyword(s):  
Deep Sea ◽  
Natural Vibration ◽  
Dominant Frequency ◽  
Bending Stress ◽  
Van Der Pol ◽  
Vibration Displacement ◽  
Vortex Induced Vibration ◽  
Towing Tank ◽  
Wake Oscillator ◽  
Shear Current

With the increase of water depth, the design and use of the top-tensioned risers (TTR) are facing more and more challenges. This research presents the effect of top tension on dynamic behavior of deep-sea risers by means of numerical simulations and experiments. First, the governing equation of vortex-induced vibration (VIV) of TTR based on Euler-Bernoulli theory and Van der Pol wake-oscillator model was established, and the effect of top tension on natural vibration of TTR was discussed. Then, the dynamic response of TTR in shear current was calculated numerically by finite difference method. The displacement, bending stress and vibration frequency of TTR with the variation of top tension were investigated. Finally, a VIV experiment of a 5 m long flexible top-tensioned model was carried out at the towing tank of Tianjin University. The results show that the vibration displacement of TTR increases and the bending stress decreases as the top tension increases. The dominant frequency of VIV of TTR is controlled by the current velocity and is barely influenced by the top tension. With the increase of top tension, the natural frequency of TTR increases, the lower order modes are excited in the same current.

End Fitting Effect on Stress Evaluation of Tensile Armor Tendons in Unbonded Flexible Pipes Under Axial Tension

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Leilei Dong ◽  
Qi Zhang ◽  
Yi Huang ◽  
Gang Liu ◽  
Zhiyuan Li
Keyword(s):  
Lateral Displacement ◽  
Axial Strain ◽  
Supplementary Condition ◽  
Bending Stress ◽  
Stress Evaluation ◽  
Axial Tension ◽  
Flexible Pipes ◽  
Helical Angle ◽  
The Wire ◽  
Unbonded Flexible Pipes

This paper deals with the effect of termination restraint due to end fitting on the stress evaluation of tensile armors in unbonded flexible pipes under axial tension. The problem is characterized by one single armoring tendon helically wound on a cylindrical supporting surface subjected to traction. The deviation from the initial helical angle is taken to describe the armor wire path as the pipe is stretched. The integral of this angle change gives the lateral displacement of the wire, which is determined by minimizing the energy functional that consists of the strain energy due to axial strain, local bending and torsion, and the energy dissipated by friction, leading to a variational problem with a variable endpoint. The governing differential equation of the wire lateral displacement, together with the supplementary condition, is derived using the variational method and solved analytically. The developed model is verified with a finite element (FE) simulation. Comparisons between the model predictions and the FE results in terms of the change in helical angle and transverse bending stress show good correlations. The verified model is then applied to study the effects of imposed tension and friction coefficient on the maximum bending stress. The results show that the response to tension is linear, and friction could significantly increase the stress at the end fitting compared with the frictionless case.

scholarly journals Failure Assessment for the High-Strength Pipelines with Constant-Depth Circumferential Surface Cracks

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
X. Liu ◽  
Z. X. Lu ◽  
Y. Chen ◽  
Y. L. Sui ◽  
L. H. Dai
Keyword(s):  
Finite Element ◽  
Practical Interest ◽  
High Strength ◽  
Influence Functions ◽  
Surface Cracks ◽  
Constant Depth ◽  
Long Distance ◽  
Integrity Assessment ◽  
Failure Assessment ◽  
Bending Loads

In the oil and gas transportation system over long distance, application of high-strength pipeline steels can efficiently reduce construction and operation cost by increasing operational pressure and reducing the pipe wall thickness. Failure assessment is an important issue in the design, construction, and maintenance of the pipelines. The small circumferential surface cracks with constant depth in the welded pipelines are of practical interest. This work provides an engineering estimation procedure based upon the GE/EPRI method to determine the J-integral for the thin-walled pipelines with small constant-depth circumferential surface cracks subject to tension and bending loads. The values of elastic influence functions for stress intensity factor and plastic influence functions for fully plastic J-integral estimation are derived in tabulated forms through a series of three-dimensional finite element calculations for different crack geometries and material properties. To check confidence of the J-estimation solution in practical application, J-integral values obtained from detailed finite element (FE) analyses are compared with those estimated from the new influence functions. Excellent agreement of FE results with the proposed J-estimation solutions for both tension and bending loads indicates that the new solutions can be applied for accurate structural integrity assessment of high-strength pipelines with constant-depth circumferential surface cracks.

A vortex induced vibration of marine riser in waves

2011 ◽  
Vol 30 (4) ◽  
pp. 96-101 ◽  
Author(s):  
Min Lou ◽  
Wenyi Dong ◽  
Haiyan Guo
Keyword(s):  
Marine Riser ◽  
Vortex Induced Vibration
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