Full Scale Fairing Qualification Tests

2015 ◽  
Author(s):  
Yiannis Constantinides ◽  
Stergios Liapis ◽  
Don Spencer ◽  
Mohammed Islam ◽  
Kjetil Skaugset ◽  
...  
Keyword(s):  
Fatigue Failure ◽  
Model Test ◽  
Hydrodynamic Performance ◽  
Documented Case ◽  
Vortex Induced Vibrations ◽  
Viv Suppression ◽  
Single Pipe ◽  
Interference Tests ◽  
Fin Design ◽  
Novel Design

Production risers as well as drilling risers are often subjected to Vortex-induced vibrations (VIV) when exposed to ocean currents. VIV have been observed in the field and can cause fatigue failure and excessive drag on the riser. In order to suppress VIV and reduce drag, fairings are often used. This paper presents hydrodynamic qualification tests for two types of fairings: the short crab claw (SCC) and a tapered dual fin design. The short crab claw fairing design is a novel design that was developed by the Norwegian Deepwater Programme (NDP). As will be detailed in this paper, the SCC design offers very low drag, completely suppresses VIV and reduces riser interference. In 2012, a model test campaign was undertaken to understand and qualify the hydrodynamic performance of fairings at prototype conditions. The program consisted of testing the three fairing geometries and a strake to understand the stand-alone performance in VIV and the performance in interference. This was accomplished by utilizing a single pipe setup for the standalone test and a two-pipe setup for the interference tests. The paper reports the results of the program and draws conclusions on the hydrodynamic performance of the VIV suppression devices tested. Overall, all VIV suppression devices tested were able to suppress VIV with the SCC fairing being the most effective. In all cases tested, the downstream fairings / strakes were very effective in suppressing VIV in an interference scenario where a fairing was placed upstream. Contrary to the well-documented case of two strakes in tandem, in this case the upstream fairings did not reduce the effectiveness of the downstream fairings/strakes.

Full-Scale Fairing Qualification Tests

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yiannis Constantinides ◽  
Stergios Liapis ◽  
Don Spencer ◽  
Mohammed Islam ◽  
Kjetil Skaugset ◽  
...  
Keyword(s):  
Model Test ◽  
Diameter Ratio ◽  
River Engineering ◽  
Scaled Model ◽  
Towing Tank ◽  
Vortex Induced Vibrations ◽  
Field Deployment ◽  
Novel Design ◽  
M 14 ◽  
Flow Splitter

Production risers as well as drilling risers are often exposed to ocean currents. Vortex-induced vibrations (VIVs) have been observed in the field and can cause fatigue failure and excessive drag on the riser. In order to suppress VIV, fairings are often used. This paper presents qualification tests for two types of fairings: the short-crab claw (SCC) fairings and the AIMS dual flow splitter (ADFS) fairings. The short-crab claw fairing design is a novel design patented by the Norwegian deepwater project (NDP). As will be detailed in this paper, both the SCC and ADFS designs offer very low drag, completely suppress VIV, and are effective even when they are in tandem. A model test campaign was undertaken in the 200-m towing tank facility at the ocean, coastal, and river engineering in St. John's, NF, Canada. A rigid pipe with a diameter of 0.3556 m (14 in) was utilized for the experiments. This corresponds to prototype size for a production riser and a 1:3.8 scaled model for a 1.3716 m (54 in) drilling riser. Given that these tests were conducted at prototype scale, they were used to qualify the fairings for field deployment. Both fairings (SCC and ADFS) were very effective in suppressing VIV and reducing drag. The ADFS fairings are most effective for a span to diameter ratio of 1.75. For all fairing geometries, it was found that a small taper increases the fairing effectiveness considerably.

Experimental Study on Flexible Bare Pipe Arrays Undergoing Vortex-Induced Vibrations

2018 ◽  
Author(s):  
Y. Liu ◽  
C. Shi ◽  
Z. Liu ◽  
J. Wang ◽  
X. Bao
Keyword(s):  
Fatigue Damage ◽  
Dynamic Responses ◽  
Array Configuration ◽  
Damage Rate ◽  
Flexible Pipes ◽  
Vortex Induced Vibrations ◽  
Helical Strakes ◽  
Preliminary Study ◽  
Single Pipe ◽  
Center Distance

Vortex-induced vibration (VIV) excited by current is a major contributor to the fatigue accumulation of marine risers. For deepwater operations, several risers are often arranged together in an array configuration. In this study, a set of four identical flexible pipes of a rectangular arrangement were tested in a water tunnel. By comparing the dynamic responses of a pipe in an array with that of a single isolated pipe, the effects of the current speed and the center-to-center distance between the up-stream and downstream pipes on their dynamic responses were investigated. Fatigue damages accumulated on each pipe in an array was calculated and a factor, termed “fatigue damage amplification factor”, was defined as a ratio between the fatigue damage rate of pipe in an array and the fatigue damage rate of a single pipe at a same current condition. The results showed that for bare pipes (i.e., without helical strakes), the downstream pipes in an array configuration may have larger dynamic responses and fatigue damage rates than those of a single pipe; and, it is not always conservative to assume that the fatigue damage rate estimated for a single pipe can be used to represent the fatigue damage rates of pipes in an array. This preliminary study provided some meaningful results for the design, analysis and operation of marine riser arrays.

Experimental Study on Hydrodynamics of Hybrid Deep-V Monohull With Different Built-Up Appendages

2018 ◽  
Author(s):  
Shuzheng Sun ◽  
Hui Li ◽  
Muk Chen Ong
Keyword(s):  
Model Test ◽  
Performance Model ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Hydrodynamic Characteristics ◽  
Vertical Acceleration ◽  
Test Results ◽  
Regular Waves ◽  
Sea State ◽  
Seakeeping Performance

The hydrodynamic characteristics of a hybrid deep-V monohull with different built-up appendages are investigated experimentally in order to improve the resistance and seakeeping performance. Model tests have been carried out to study the hydrodynamic performance between a bare deep-V vessel and a deep-V monohull with different built-up appendage configurations (i.e. a hybrid deep-V monohull). From the model test results, it is found that the existence of the appendages will reduce the amplitude of pitching angle and bow vertical acceleration compared to that of the bare deep-V vessel in heading regular waves. However, the resistances for the hybrid deep-V monohull with built-up appendages are increased 15.6% for Fn = 0.264, and 0.1% for Fn = 0.441 compared to the resistance of the bare deep-V vessel. The model test results of seakeeping performance in irregular waves show that the hybrid deep-V monohull gives a better seakeeping performance than the deep-V vessel. The pitching angle and bow vertical acceleration of the hybrid deep-V monohull containing a built-up appendage are reduced 15.3% and 20.6% compared to the deep-V monohull in irregular waves at Fn = 0.441 in 6th class sea state (H1/3 = 6m).

Fairing Evaluation Based on Numerical Simulation

2012 ◽  
Author(s):  
Juan P. Pontaza ◽  
Mohan Kotikanyadanam ◽  
Piet Moeleker ◽  
Raghu G. Menon ◽  
Shankar Bhat
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Current Speed ◽  
Full Scale ◽  
Attractive Alternative ◽  
Element Analysis ◽  
Vortex Induced Vibrations ◽  
Helical Strakes ◽  
Computational Fluid Dynamics Cfd ◽  
Viv Suppression

It is well established that strakes are effective at suppressing vortex-induced vibrations (VIV). Fairings are an attractive alternative to helical strakes, because they are a low drag VIV suppression solution. The paper presents an evaluation of a fairing design, based on numerical simulations — to be complemented at a later stage with current tank testing. This paper documents the computational fluid dynamics (CFD) and finite element analysis (FEA) of the evaluation: (1) 3-D CFD in the laboratory scale: 4.5 inch pipe, 3 ft/s current speed, (2) 3-D CFD in the full scale: 14 inch riser, 4 knots current speed, and (3) 3-D FEA of the full-scale fairing module latching mechanism, under service loads corresponding to 4 knots current speed. The analysis results show that the fairing design (1) is effective at suppressing VIV, (2) yields a low drag coefficient (0.52 at Re ∼ 106), and (3) its latching mechanism is adequate for use in calm sea states with 4 knots current speeds.

Model Testing for Vortex Induced Motions of Spar Platforms

2004 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Gulf Of Mexico ◽  
Model Test ◽  
State Of The Art ◽  
Model Testing ◽  
Model Tests ◽  
The State ◽  
Test Results ◽  
Test Set ◽  
Vortex Induced Vibrations ◽  
Set Up

The state-of-the art in model testing for Vortex Induced Vibrations (VIV) of Spars is presented. Important issues related to Spar VIV model testing are highlighted. The parameters that need to be modeled including hull geometry, strake configuration, mass and mooring properties and, considerations of test set-up and instrumentation are discussed. Results are presented from model tests of an as-built Spar deployed in the Gulf of Mexico. It is shown that the model test results compare well with the VIV responses measured in the field.

Study of Tandem Offloading System for a New Concept Spar FPSO

2014 ◽  
Author(s):  
Wei Gao ◽  
Xiaoliang Qi ◽  
Jin Wang
Keyword(s):  
South China Sea ◽  
Numerical Simulations ◽  
Model Test ◽  
South China ◽  
Time Domain ◽  
Oil Field ◽  
Hydrodynamic Performance ◽  
China Sea ◽  
Oil Storage ◽  
Tandem Offloading

A new concept Spar FPSO (Floating Production Storage and Offloading) is proposed for South China Sea deepwater oil field development integrating the advantages of the deep-draft Spar concept whose excellent stability and global performance enables dry-tree drilling and production, and the conventional ship-shaped FPSO for oil storage and offloading. This paper presents a study of the tandem offloading system for the new concept Spar FPSO. The paper will first give an overview of various offloading configurations and their characteristics for deepwater development; then a tandem offloading system similar to conventional ship-shaped FPSO is recommended for further investigation considering operational experience, safety and economical benefits. As the offloading operations are generally weather-limited, offloading environmental conditions for the study are selected based on API, ABS and South China Sea offshore operation practices. For a case study, hydrodynamic performance of the Spar FPSO in tandem offloading configuration with a shuttle tanker in 1500m water depth was investigated numerically and experimentally. Numerical simulations were conducted by means of fully coupled nonlinear time-domain analysis. The distance between the shuttle tanker and the Spar FPSO is optimized based on the relative motions of the two floaters and the hawser tension requirement of the shuttle tanker. Experimental results from model test are presented and compared with analytical time-domain simulation results. It is shown that the results of numerical simulations are consistent with the model test. The tandem offloading system demonstrates robust performance and cost-effectiveness for the proposed Spar FPSO concept.

Suppression of Vortex Induced Vibrations of Circular Cylinders Using Radial Water Jets

2002 ◽  
Author(s):  
Kjetil B. Skaugset ◽  
Carl M. Larsen
Keyword(s):  
Flow Pattern ◽  
Volume Flow Rate ◽  
Ocean Current ◽  
Cylinder Surface ◽  
Cylinder Wall ◽  
Local Pressure ◽  
Water Jets ◽  
Vortex Induced Vibrations ◽  
Operational Life ◽  
Viv Suppression

For oilfield developments in deep water, it is of utmost importance to accurately predict vortex induced vibrations (VIV) of risers and free span pipelines subjected to ocean current. In order to prolong operational life of such structures, VIV suppression devices such as helical strakes or shrouds are often employed. Such devices will, however, imply certain disadvantages such as drag amplification and increased operational costs. Therefore the quest for effective suppression devices with a minimum of such drawbacks is still ongoing. The present paper presents a novel approach for VIV suppression based on radial water jets from a prescribed pattern of circular openings in the cylinder wall. Jet flow will introduce a disturbance that will change VIV amplitudes. The alternation of the flow pattern must be understood to have both 2-dimensional (2-D) and 3-D effects. 2-D effects will influence the local pressure on the cylinder surface by altering the separation point as well as creating a general disturbance to the flow, while the 3-D effects involve changes in correlation of the vortex shedding process along the span of the cylinder. The disturbance to the flow pattern is expected to yield reduced VIV amplitudes. Results will be presented from experiments in a towing tank testing three 2m long spring supported cylinders with diameter 0.1m and two different patterns of radial water jets. The volume flow rate and reduced velocity have been varied in the tests. Oscillation amplitudes, frequencies, added mass and lift and drag force coefficients are presented and compared to a smooth cylinder.

The Axial Distribution of Gas Hold-Up and Solid Concentration in Slurry Reactor and its Effect to the Design of Slurry Reactor

2012 ◽  
Vol 560-561 ◽  
pp. 606-613
Author(s):  
Shao Hua Jiang ◽  
Yao Bin Chen
Keyword(s):  
Model Test ◽  
Synthesis Gas ◽  
Slurry Reactor ◽  
Productive Capacity ◽  
Solid Concentration ◽  
Cold Model ◽  
Axial Distribution ◽  
Step Process ◽  
One Step ◽  
Novel Design

The axial distribution of gas hold-up and solid concentration in the slurry reactor are studied by the cold-model test, the principle of distribution is got. Furthermore, a new concept, fresh gas hold-up is put forward. As to the process of DME from synthesis gas by one-step process in the slurry reactor, according to the principle of axial distribution of gas hold-up and solid concentration in the reactor, the author put forward a novel design of the slurry, thus the space of the reactor is used fully, the reactive conversion can be raised, the productive capacity of reactor also can be raised.

Model Test Experience on Vortex Induced Vibrations of Truss Spars

2003 ◽  
Author(s):  
Radboud van Dijk ◽  
Allan Magee ◽  
Steve van Perryman ◽  
Joe van Gebara
Keyword(s):  
Model Test ◽  
Vortex Induced Vibrations

The Research of Moonpool Size Effect on the Hydrodynamic Performance of FDPSO

2011 ◽  
Author(s):  
Yuefeng Wei ◽  
Jianmin Yang ◽  
Gang Chen ◽  
Zhiqiang Hu
Keyword(s):  
Numerical Analysis ◽  
Size Effect ◽  
White Noise ◽  
Natural Frequency ◽  
Model Test ◽  
Hydrodynamic Performance ◽  
Ocean Engineering ◽  
Floating Platform ◽  
Paper Making ◽  
Reliable Model

FDPSO is a multifunction floating platform, which has the combined function of drilling, production, storage and offloading oil. The moonpool is necessary for drilling operation and the moonpool size effect will play a role on the hydrodynamic performance of FDPSO. A study of the moonpool size effect on such performance of FDPSO hull is presented in this paper, making use of numerical analysis and model tests techniques. The code WADAM is used for the hydrodynamic performance analysis. A model test aiming to validate the accuracy of the numerical analysis results was conducted in the Ocean Engineering basin in the State Key Laboratory of Ocean Engineering in the Shanghai Jiao Tong University. The model test included decaying test and white noise test. The decaying tests are performed in still water for heave, roll and pitch. White noise tests were carried out to obtain the RAO of FDPSO, with the wave incoming direction of 180° and 135°. The numerical results show a good agreement with the model test results, indicating a reliable model. The “piston” motion of the water inside the moonpool is significant, affecting the hydrodynamic performance of the FDPSO. The effect of moonpool size on the hydrodynamic performance of the FDPSO is analyzed through a numerical method. The relationship between the piston natural frequency of the water column inside the moonpool and its diameter and draft, are studied. An empirical formula of the “piston” natural frequency is proposed, and its validity is assessed.

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