Experimental Study of the Effect of the Pontoon Dimensions on the Flow-Induced Motions (FIM) of a Semi-Submersible Platform With Four Square Columns

2020 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
Hideyuki Suzuki ◽  
Matheus A. Marques ◽  
Leandro S. P. Silva ◽  
Chenling Tian ◽  
...  
Keyword(s):  
Experimental Study ◽  
Fatigue Life ◽  
Transverse Direction ◽  
Vertical Direction ◽  
Model Tests ◽  
Mooring Line ◽  
Towing Tank ◽  
Spacing Ratio ◽  
Floating System ◽  
Four Square

Abstract The Flow-Induced Motions (FIM) is an essential topic on multi-column platforms due to the effect on the mooring line fatigue life. Vortex-Induced Motions (VIM) or galloping behavior can be observed for an array of four columns with square sections. The presence of pontoons showed to be important for changing the flow around the array and promoting different amplitude behaviors of the motions in the transverse direction mainly. This article aims to understand the effect of the presence of four pontoons on the FIM of a semi-submersible platform (SS) with four square section columns. Model tests of a floating system supported elastically utilizing four springs were performed in a towing tank. Five different pontoon ratios were tested, namely P/L = 0, 0.25, 0.50, 0.75, and 1.00; where P is the pontoon height (the dimension in the vertical direction), and L is the length of the square column face. The draft condition was kept constant as H/L = 1.5; where H is the draft of the platform. The spacing ratio of the columns was S/L = 4; where S is the distance between column centers. Two incidence angles of the current were carried out, namely 0 and 45 degrees. The amplitudes in the transverse direction (direction perpendicular to the incidence current) decreased by increasing the pontoon ratio for 0 and 45-deg incidences. The pontoons positioned aligned to the flow significantly reduced the amplitudes in the transverse direction since the pontoon presence in this position modified the incident wake in the downstream columns. The pontoon presence needs to be well investigated to choose the best condition to avoid raising the FIM or mitigating the FIM.

Experimental Study of the Effect of the Pontoon Presence on the Flow-Induced Motion of a Semi-Submersible Platform With Four Square Columns

2019 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
Hideyuki Suzuki ◽  
Fredi Cenci ◽  
André L. C. Fujarra ◽  
Shinichiro Hirabayashi
Keyword(s):  
Experimental Study ◽  
Fatigue Life ◽  
Transverse Direction ◽  
The Other ◽  
Mooring Line ◽  
Towing Tank ◽  
Spacing Ratio ◽  
Floating System ◽  
Induced Motion ◽  
Four Square

Abstract The Flow-Induced Motions (FIM) is an essential topic on multi-column platforms due to the effect on the mooring line fatigue life. Vortex-Induced Motions (VIM) or galloping behavior can be observed for an array of four columns with square sections. The presence of pontoons showed to be important for changing the flow around the array and promote different amplitude behavior of the motions in the transverse direction mainly. This article aims to understand the effect of the presence of two pontoons on the FIM of a semi-submersible platform (SS) with four columns and square sections. Model tests of a floating system supported elastically utilizing four springs were performed in a towing tank. Five different pontoon ratios were tested, namely P/L = 0, 0.25, 0.50, 0.75 and 1.00; where P is the pontoon height, and L is the length of the square column face. The draft condition was kept constant as H/L = 1.5; where H is the draft of the platform. The spacing ratio of the columns was S/L = 4; where S is the distance between column centers. Three incidence angles of the current were carried out, i.e., 0-deg incidence represents the condition in which the two pontoons are aligned to the current, 45-deg incidence represents the non-symmetric condition in which the pontoons are 45 degrees positioned to the current, and 90-deg incidence represents the condition in which the two pontoons are perpendicular to the current. The transverse amplitudes decreased with increasing the pontoon ratio for 0 and 45-deg incidences. On the other hand, the transverse amplitudes increased with increasing the pontoon ratio for 90-deg incidence. The pontoon presence needs to be well investigated to choose the best condition to avoid raising the FIM.

Study on vertical motion reduction of a trimaran based on collaborative controlled appendages

2020 ◽  
Vol 17 (6) ◽  
pp. 172988142097677
Author(s):  
Zhilin Liu ◽  
Linhe Zheng ◽  
Guosheng Li ◽  
Shouzheng Yuan ◽  
Songbai Yang
Keyword(s):  
Experimental Study ◽  
Vertical Motion ◽  
Model Tests ◽  
Wave Period ◽  
Regular Waves ◽  
Towing Tank ◽  
Vertical Stability ◽  
Stabilization Control ◽  
Stability Performance

In recent years, the trimaran as a novel ship has been greatly developed. The subsequent large vertical motion needs to be studied and resolved. In this article, an experimental study for a trimaran vertical stabilization control is carried out. Three modes including the bare trimaran (the trimaran without appendages, the trimaran with fixed appendages, and the trimaran with controlled appendages) are performed through model tests in a towing tank. The model tests are performed in regular waves. The range of wave period is 2.0–4.0 s, and the speed of the carriage is 2.93 and 6.51 m/s. The results of the three modes show the fixed appendages and the actively controlled appendages are all effective for the vertical motion reduction of the trimaran. Moreover, the controlled appendages are more effective for the vertical stability performance of the trimaran.

Experimental Study of a Tanker Ship Squat in Shallow Water

2014 ◽  
Vol 66 (2) ◽  
Author(s):  
Mohammadreza Fathi Kazerooni ◽  
Mohammad Saeed Seif
Keyword(s):  
Experimental Study ◽  
Shallow Water ◽  
Experimental Approach ◽  
Model Tests ◽  
Ship Hull ◽  
Experimental Results ◽  
Shallow Waters ◽  
Towing Tank ◽  
Ship Model

One of the phenomena restricting the tanker navigation in shallow waters is reduction of under keel clearance in the terms of sinkage and dynamic trim that is called squatting. According to the complexity of flow around ship hull, one of the best methods to predict the ship squat is experimental approach based on model tests in the towing tank. In this study model tests for tanker ship model had been held in the towing tank and squat of the model are measured and analyzed. Based on experimental results suitable formulae for prediction of these types of ship squat in fairways are obtained.

Riser VIM Fatigue Design Induced by Deep Draft Semi-Submersible

2010 ◽  
Author(s):  
Sherry Xiang ◽  
Peimin Cao ◽  
Oriol Rijken ◽  
Jian Ma ◽  
Yongjun Chen
Keyword(s):  
Gulf Of Mexico ◽  
Transfer Functions ◽  
Sensitivity Study ◽  
Model Tests ◽  
Mooring Line ◽  
Simplified Approach ◽  
Fatigue Design ◽  
South Central ◽  
Four Square ◽  
The Impact

SBM Atlantia Inc. (SBMA) designs and constructs DeepDraft Semi® Floating Production Units (FPU). Two of these units are installed in the South-Central Gulf of Mexico at water depths of 8,000-ft and 6,000-ft. Both units are operational. Each of these FPUs is characterized by four square columns interconnected by four rectangular pontoons. Model tests and field measurements have indicated that these types of vessels are susceptible to Vortex Induced Motions (VIM). Typical loop/eddy current conditions at these Gulf of Mexico locations are likely to induce semi FPU VIM response. The paper addresses the impact of the semi-submersible FPU VIM motion on the fatigue design of the Steel Catenary Risers (SCR). Semi VIM induced riser fatigue design is performed using time domain approach and the scatter diagrams for the surface currents. Riser fatigue damage rates consider the effects of both the inline and transverse semi VIM responses. A comprehensive sensitivity study has been carried out, and the results demonstrate that riser VIM fatigue is primarily affected by the combination of column shape, current heading and intensity, the individual riser configuration, mooring line pretention and polyester stiffness. A simplified approach based on quasi-static Stress Transfer Functions (STF) is proposed. The STF is developed based on the VIM motion amplitude without considering the effect of the mean FPU offset induced by the current. The STF allows one to quickly develop a preliminary map identifying the feasible riser configurations. Such map can be used during the Front End Engineering Design (FEED) studies to initiate viable riser configurations. Finally, it is important to note that the preliminary field VIM measurements are significantly less than those observed during the model tests. Therefore, the fatigue life estimates based on the model test observations are considered to be conservative.

Model Tests on Additional Stress Transmission between Different Granular Materials in Foundation Soils

2014 ◽  
Vol 919-921 ◽  
pp. 828-834
Author(s):  
Chang Dan Wang ◽  
Shun Hua Zhou ◽  
Hui Su
Keyword(s):  
Granular Materials ◽  
Boundary Surface ◽  
Vertical Direction ◽  
Stress Transfer ◽  
Fine Sand ◽  
Compression Modulus ◽  
Model Tests ◽  
Additional Stress ◽  
Stress Transmission ◽  
Different Soils

To research and analyze the additional stress distribution and change of granular materials, the model tests are used to observe vertical additional stress in different position and depth in different foundations. And the comparison between observed values both in different soils and single soils is conducted to analyze the transmission and attenuation of additional stress in granular materials. The research results show that the existing of boundary surface can lead to different vertical additional stress transmit obviously. And with the increasing of loading, the vertical additional stress differences between that of different soils get larger, meanwhile, the ratio of stress differences to smaller additional stress increases slightly. With the increasing of depth, the attenuation rate of vertical additional stress of silty soil changes much fast than that of fine sand. Wherever in horizontal direction or vertical direction, the vertical additional stress of fine sand which has higher compression modulus in different soils is slightly larger than that in single soil and transfers additional stress (loading) more under the same loading. To granular materials, inner friction structure effect is evident influence to additional stress transfer.

Experimental Analysis of Five Keel-Hull Combinations

1985 ◽  
Author(s):  
J. Gerritsma ◽  
J. A. Keuning
Keyword(s):  
Experimental Analysis ◽  
Model Tests ◽  
Experimental Results ◽  
Forward Speed ◽  
Hull Form ◽  
Towing Tank ◽  
Side Force ◽  
Performance Predictions

Model tests with five different keels in combination with one particular hull form have been carried out in the Delft Towing Tank. The variations include a plain deep keel, a keel-centre board, a plain restricted draft keel,a "Scheel" keel and a "winglet" keel. Based on the experimental results performance predictions are given for a 63 ft yacht for windspeeds up to 25 knots. The measured side force and resistance as a function of heeling angle, leeway angle and forward speed are used to analyse the relative merits of the considered keel-hull combinations.

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