Experimental Determination of Resonant Response in the Narrow Gap Between Two Side-by-Side Fixed Bodies in Deep Water

2016 ◽  
Author(s):  
Wenhua Zhao ◽  
Hugh Wolgamot ◽  
Scott Draper ◽  
Paul H. Taylor ◽  
Rodney Eatock Taylor ◽  
...  
Keyword(s):  
White Noise ◽  
Numerical Simulations ◽  
Water Depth ◽  
Deep Water ◽  
Model Tests ◽  
Full Scale ◽  
Resonance Phenomenon ◽  
Resonant Response ◽  
Gap Resonance ◽  
Wave Basin

Floating liquefied natural gas (FLNG) facilities are a new type of offshore structure, which have been developed as a game changer in offshore hydrocarbon development for unlocking stranded gas reserves. One of the key challenges associated is offloading from FLNG facilities to LNG carriers. Offloading may proceed with vessels in a side-by-side configuration, which allows offtake by un-modified vessels and minimizes requirements for new hardware or procedures (e.g. compared to a tandem operation). Significant challenges remain, however, and reliable offloading is critical for successful FLNG implementation. In this scenario, the two vessels are separated by a narrow 4 m wide gap. The resonant response of the sea surface in the gap has been predicted by numerical simulations [1] to be a few times that of the incident waves at particular frequencies. As a consequence, the gap resonant response may play a role in determining the operational window for side-by-side offloading operations, and thus has attracted a lot of attention recently. There have been studies on this topic both numerically and experimentally. However, many of these studies are in 2 dimensions (2D), for relatively large gaps and relatively shallow water depth, which may pose difficulties when extending the results to a real project. It is unclear what will happen for a gap resonance if the gap width gets narrower (say 4 m in full scale) and the water depth gets deeper (say 600 m in full scale). In this study, we conducted a series of model tests at a scale of 1:60 in a large wave basin, and focused on deep water and, crucially, narrow gaps, which are closer to a real project geometry. To facilitate future numerical simulations, we used two identical fixed bodies in the model tests and the vessels were simple barge-like shapes. Using white noise waves as the excitation, which covers a broad brand, the response of the fluid in the gap has been measured at several points. In these experiments, different modes of the gap resonance have been observed. Response amplitude operators (RAOs) of the gap resonance have been obtained through spectral analyses, which provide valuable information for the design of side-by-side operations and will benefit future numerical simulations. Test runs in white noise waves with different significant wave heights were also performed, to study the nonlinearities of the gap resonance phenomenon.

Resistance Tests of an Articulated Pusher Barge System in Deep and Shallow Water

2021 ◽  
Author(s):  
Li Zhang ◽  
Lei Xing ◽  
Mingyu Dong ◽  
Weimin Chen
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Deep Water ◽  
Water Resistance ◽  
Model Tests ◽  
System 2 ◽  
Changing Trend ◽  
The Difference ◽  
Transport Vessel ◽  
Resistance Performance

Abstract Articulated pusher barge vessel is a short-distance transport vessel with good economic performance and practicability, which is widely used in the Yangtze River of China. In this present work, the resistance performance of articulated pusher barge vessel in deep water and shallow water was studied by model tests in the towing tank and basin of Shanghai Ship and Shipping Research Institute. During the experimental investigation, the articulated pusher barge vessel was divided into three parts: the pusher, the barge and the articulated pusher barge system. Firstly, the deep water resistance performance of the articulated pusher barge system, barge and the pusher at design draught T was studied, then the water depth h was adjusted, and the shallow water resistance at h/T = 2.0, 1.5 and 1.2 was tested and studied respectively, and the difference between deep water resistance and shallow water resistance at design draught were compared. The results of model tests and analysis show that: 1) in the study of deep water resistance, the total resistance of the barge was larger than that of the articulated pusher barge system. 2) for the barge, the shallow water resistance increases about 0.4–0.7 times at h/T = 2.0, 0.5–1.1 times at h/T = 1.5, and 0.7–2.3 times at h/T = 1.2. 3) for the pusher, the shallow water resistance increases about 1.0–0.4 times at h/T = 2.7, 1.2–0.9 times at h/T = 2.0, and 1.7–2.4 times at h/T = 1.6. 4) for the articulated pusher barge system, the shallow water resistance increases about 0.2–0.3 times at h/T = 2.0, 0.5–1.3 times at h/T = 1.5, and 1.0–3.5 times at h/T = 1.2. Furthermore, the water depth Froude number Frh in shallow water was compared with the changing trend of resistance in shallow water.

Development of Deep Water Multicolumn Buoy

2014 ◽  
Author(s):  
Rodrigo A. Barreira ◽  
Vinicius L. Vileti ◽  
Joel S. Sales ◽  
Sergio H. Sphaier ◽  
Paulo de Tarso T. Esperança
Keyword(s):  
Conceptual Design ◽  
Water Depth ◽  
Deep Water ◽  
Model Tests ◽  
Optimization Process ◽  
Life Duration

A new conceptual design of a deepwater MONOBUOY, named DeepWater MultiColumn Buoy (DWMCB), patent PCT/BR2011/000133, was developed by PETROBRAS/CENPES. The DWMCB was designed to be part of an offloading system for a Spread Moored Floating Production Offloading Unit (FPSO). The offloading system principle consists of Oil being exported from the FPSO to a Shutle tanker passing through Offloading Oil Lines (OOLs) that are supported by the DWMCB. The system is designed to operate at a water depth of 2,200 meters, with expected in site life duration of 25 years. The geometry of DWMCB was defined after an optimization process in order to minimize its motions. This paper describes the development of this concept and discusses the results from some design verifications done with the help of a model tests campaign. An equivalent traditional shaped monobuoy was also tested for comparison purposes.

FourStar™ Dry-Tree Semisubmersible Development

2010 ◽  
Author(s):  
Neil Williams ◽  
Steve Leverette ◽  
Sean Bian ◽  
Sean Large ◽  
Peimin Cao
Keyword(s):  
Water Depth ◽  
Model Tests ◽  
Wave Basin

This paper discusses the development of a dry-tree semisubmersible (DTS) platform concept appropriate for deployment in non-hurricane/non-cyclonic environments worldwide, and the verification of the concept through wave basin model tests. An example configuration is presented for an application in 2,100 m water depth offshore Brazil.

Experimental study on effect of side-mooring lines on dynamics of a catenary moored semi-submersible system

2019 ◽  
Vol 234 (1) ◽  
pp. 127-142
Author(s):  
Sheng Xu ◽  
Chun-yan Ji ◽  
C Guedes Soares
Keyword(s):  
White Noise ◽  
Model Tests ◽  
Noise Model ◽  
Floating Platform ◽  
Mooring Lines ◽  
Motion Response ◽  
Free Decay ◽  
Wave Basin ◽  
White Noise Model ◽  
Response Amplitude Operators

In this article, a novel mooring system with side-mooring lines is proposed for a traditional shape semi-submersible platform with four columns. To obtain the dynamics of moored system, model tests were carried out at a wave basin, including free-decay model tests, white noise model tests and irregular model tests. The natural periods in heave, roll and pitch models were measured and compared with numerical results. The motion response amplitude operators under 90° and 135° waves were obtained from white noise model tests and then compared with numerical simulations. A 100-year sea state in South China Sea was simulated in the wave basin by the JONSWAP spectrum, and the 6-degree-of-freedom motion responses of semi-submersible and mooring tensions were recorded in beam and quartering seas. The effects of the side-mooring lines on the floating platform motion response, mooring tensions and mooring fatigue damage are evaluated by comparing the results with and without side-mooring lines installed.

Influence of the Rotor Characterization on the Motion of a Floating Wind Turbine

2015 ◽  
Author(s):  
Sébastien Gueydon ◽  
Guillaume Venet ◽  
Gerson Fernandes
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Rotation Speed ◽  
Model Tests ◽  
Full Scale ◽  
Aerodynamic Damping ◽  
Common Solution ◽  
Floating Wind Turbine ◽  
Wave Basin ◽  
Low Reynolds

It is useful to complement model tests of a floating wind turbine with simulations mimicking the scaled-down turbine. Standard engineering tools have some short-comings to model a rotor at the very low Reynolds that Froude scaled wind and rotor’s rotation speed impose. The flow around an airfoil at the scale of a wave basin brings new distinct challenges than at full scale. The capacity of standard engineering tools for the design of wind turbines to capture this complexity may be questioned. Therefore, work-around solutions need to be proposed. This paper looks at a common solution that consists of optimizing the load coefficients of the rotor to reproduce the measured rotor loads. 3 variants of optimizations are applied to a semisubmersible floating wind turbine at scale 1/50th, the DeepCwind semisubmersible platform. The effects of the differences between these 3 methods on the motions of the floater in waves and wind are analyzed. In the absence of a controller for the rotor, no significant differences related to the induced aerodynamic damping was noticed, but an offset in the motion related to a thrust deficit was observed.

Experimental and Numerical Study on Large Truncation of Deepwater Mooring Line

2009 ◽  
Author(s):  
Yihua Su ◽  
Jianmin Yang ◽  
Longfei Xiao ◽  
Gang Chen
Keyword(s):  
Dynamic Response ◽  
Water Depth ◽  
Numerical Study ◽  
Unit Length ◽  
Low Frequency ◽  
Model Tests ◽  
Mooring Line ◽  
Mooring System ◽  
Mooring Lines ◽  
Wave Basin

Modeling the deepwater mooring system in present available basin using standard Froude scaling at an acceptable scale presents new challenges. A prospective method is to truncate the full-depth mooring lines and find an equivalent truncated mooring system that can reproduce both static and dynamic response of the full-depth mooring system, but large truncation arise if the water depth where the deepwater platform located is very deep or the available water depth of the basin is shallow. A Cell-Truss Spar operated in 1500m water depth is calibrated in a wave basin with 4m water depth. Large truncation arises even though a small model scale 1:100 is chosen. A series of truncated mooring lines are designed and investigated through numerical simulations, single line model tests and coupled wave basin model tests. It is found that dynamic response of the truncated mooring line can be enlarged by using larger diameter and mass per unit length in air. Although the truncated mooring line with clump presents a “taut” shape, its dynamic characteristics is dominated by the geometry stiffness and it underestimates dynamic response of the full-depth mooring line, even induces high-frequency dynamic response. There are still two obstacles in realizing dynamic similarity for the largely truncated mooring system: lower mean value of the top tension of upstream mooring lines, and smaller low-frequency mooring-induced damping.

Analysis of Catenary Mooring Systems Based on Truncated Mooring Experiments

2018 ◽  
Author(s):  
Sheng Xu ◽  
Chunyan Ji ◽  
C. Guedes Soares
Keyword(s):  
Water Depth ◽  
Model Tests ◽  
Mooring System ◽  
Coupled Dynamic Analysis ◽  
Motion Responses ◽  
Wave Basin ◽  
Six Dof ◽  
Floating Systems ◽  
Fully Coupled ◽  
Reasonable Model

Considering the activities of floating systems pushing to the ultra-deepwater, the full scale mooring system needs to be truncated in order to carry out model tests in wave basin with reasonable model scale. In this paper, a Semi-Submersible moored by a catenary mooring system, which operates in 1500m water depth is truncated at 200m water depth. The mooring induced damping of truncated mooring system and prototype mooring system in 100 year typhoon condition in South China Sea are studied experimentally and numerically. The de-couple technique is applied to obtain truncated mooring damping, which is implemented by inputting the vessel six DOF motion responses and solving the mooring tensions, then decompose mooring tension in x, y and z directions. The vessel six DOF motion responses were measured in the model tests. For the full depth mooring system, the fully coupled dynamic analysis is carried out to study mooring induced damping. The results of truncated mooring damping will be compared with full depth mooring damping.

Performance of a Covering Pipe for the Protection of Underwater Cable Subjected to on-Site Impact Loadings

2011 ◽  
Vol 82 ◽  
pp. 810-815
Author(s):  
Hsien Hua Lee
Keyword(s):  
Cast Iron ◽  
Water Depth ◽  
Deep Water ◽  
Experimental Studies ◽  
Experimental Tests ◽  
Full Scale ◽  
Scale Model ◽  
Local Power ◽  
Pipe System ◽  
Power Company

In this study, a protection-pipe system has been developed for the protection of undersea electricity cable layout along shoreline with medium deep water. The protection pipes are made of cast-iron alloys while the dimensions are designed corresponding to the balk diameter of electricity cables. The water depth of the area with cable layout is ranged from several meters to a hundred meters, where berthing anchoring from commercial ships and towing operation from fishing boats are constantly found. Therefore, to make sure that the protection pipe can work dependably against the loadings mainly from the operation as was mentioned, both analytical analysis and experimental tests were carried out. In the experimental studies, the full-scale model of several sets of protection-pipe system was tested for impact loadings. It was found from the results of both the analysis and experimental tests that the protection-pipes are able to meet the requirements of the local power company TPC set for the cable layout under seawater.

Design and Testing of Scale Model Wind Turbines for Use in Wind/Wave Basin Model Tests of Floating Offshore Wind Turbines

2013 ◽  
Author(s):  
Matthew J. Fowler ◽  
Richard W. Kimball ◽  
Dale A. Thomas ◽  
Andrew J. Goupee
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Model Tests ◽  
Full Scale ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Wave Basin ◽  
Scale Design

Model basin testing is a standard practice in the design process for offshore floating structures and has recently been applied to floating offshore wind turbines. 1/50th scale model tests performed by the DeepCwind Consortium at Maritime Research Institute Netherlands (MARIN) in 2011 on various platform types were able to capture the global dynamic behavior of commercial scale model floating wind turbine systems; however, due to the severe mismatch in Reynolds number between full scale and model scale, the strictly Froude-scaled, geometrically similar wind turbine underperformed greatly. This required significant modification of test wind speeds to match key wind turbine aerodynamic loads, such as thrust. To execute more representative floating wind turbine model tests, it is desirable to have a model wind turbine that more closely matches the performance of the full scale design. This work compares the wind tunnel performance, under Reynolds numbers corresponding to model test Froude-scale conditions, of an alternative wind turbine designed to emulate the performance of the National Renewable Energy Laboratory (NREL) 5 MW turbine. Along with the test data, the design methodology for creating this wind turbine is presented including the blade element momentum theory design of the performance-matched turbine using the open-source tools WT_Perf and XFoil. In addition, a strictly Froude-scale NREL 5 MW wind turbine design is also tested to provide a basis of comparison for the improved designs. While the improved, performance-matched turbine was designed to more closely match the NREL 5 MW design in performance under low model test Reynolds numbers, it did not maintain geometric similitude in the blade chord and thickness orientations. Other key Froude scaling parameters, such as blade lengths and rotor operational speed, were maintained for the improved designs. The results of this work support the development of protocols for properly designing scale model wind turbines that emulate the full scale design for Froude-scale wind/wave basin tests of floating offshore wind turbines.

Ultra-Deepwater Model Testing of a Semisubmersible and Hybrid Verification

2008 ◽  
Author(s):  
Timothy E. Kendon ◽  
Ola Oritsland ◽  
Rolf J. Baarholm ◽  
Svein I. Karlsen ◽  
Carl-Trygve Stansberg ◽  
...  
Keyword(s):  
Model Test ◽  
Water Depth ◽  
Deep Water ◽  
Low Frequency ◽  
Line Tension ◽  
Model Tests ◽  
Test Results ◽  
Test Verification ◽  
Good Agreement

Model test verification of floater systems in ultra-deep water meets limitations when it comes to available laboratory sizes. Systems in depths beyond 1000–1500 m cannot be tested at reasonable scales without the truncation of the mooring and riser system. The development of methods and procedures to overcome this problem has been addressed through extensive research programs at MARINTEK (VERIDEEP, VERIDEEP Extension, NDP, DEMO2000). This led to a hybrid verification procedure which combines reasonable truncation principles, model tests of the truncated system, and numerical simulations, to estimate the system’s response at full depth. There is, however, still a need to address the actual influence from the truncation procedure, and from the integration with simulations, on the final extrapolated full depth results. This paper presents a case study for the validation of the procedure, that compares full depth model test results of a semisubmersible in water depth 1250m against the extrapolated full depth results obtained from a truncated system of 500m. Results are presented for line tension and vessel responses in 3 seastates. In general the extrapolated full depth results were found to be in good agreement with the full depth model tests. However, the results confirmed expectation that the low frequency response has the greater uncertainties and presents the greatest challenge for the procedure.

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