Experimental Study Into Vortex Induced Motion Response of Semi Submersibles With Square Columns

2008 ◽  
Author(s):  
Oriol Rijken ◽  
Steven Leverette
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Mooring System ◽  
Test Program ◽  
Sea State ◽  
Response Characteristics ◽  
Test Conditions ◽  
Induced Motion ◽  
Four Square ◽  
Model Programs

Vortex Induced Motion (VIM) of a Deep Draft Semi® with four square columns has been observed in model tests and in a prototype configuration. The flow field around the columns causes the vessel to oscillate along one of the vessel’s main diagonals under particular conditions. The observations and conclusions of three series of VIM model programs are combined in this report. Each test program was executed with a unique objective in mind and each setup was unique. Many similarities in response characteristics have been identified. Some of the differences in observed response are identified and discussed. A discussion is provided regarding the scaling of VIM problems, and the importance of the Reynolds number under model test conditions is discussed. The VIM of a typical Gulf of Mexico Deep Draft Semi® may affect the fatigue life of the mooring system and risers. A formulation is developed that predicts the distribution of VIM amplitudes which then can be used to estimate VIM induced fatigue damage. Observations and conclusions are provided of several experiments where VIM response was evaluated in the presence of a fatigue sea state and for a system with increased sway damping.

Experimental Investigations Into the Influences of SCRs and Appurtenances on Deepdraft Semisubmersible Vortex Induced Motion Response

2011 ◽  
Author(s):  
Oriol Rijken ◽  
Sipke Schuurmans ◽  
Steve Leverette
Keyword(s):  
Experimental Study ◽  
Model Test ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Mooring System ◽  
Motion Response ◽  
Test Conditions ◽  
Induced Motion ◽  
Scr System ◽  
Design Guidance

Vortex Induced Motion (VIM) response of a deep draft semisubmersible with square columns has been observed various model test conditions and in the field. A good understanding of the VIM phenomenon is desired because VIM can lead to significant SCR fatigue, especially for the larger diameters SCRs. A VIM design guidance was developed from several previous experimental investigations. Those experimental investigations are characterized by hulls with limited detail, and a simplified mooring / SCR system where typically only the stiffness is taken into consideration. A comparative experimental study is performed to identify the differences in VIM response under the absence and presence of hull appurtenances. Further, the VIM responses of a semisubmersible restrained by a mooring system without and with an SCR system are compared. An evaluation of the experimental results leads to an improved understanding of the VIM response at model test scale.

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.

Wave Effects on Vortex-Induced Motion (VIM) of a Large-Volume Semi-Submersible Platform

2012 ◽  
Author(s):  
Rodolfo T. Gonçalves ◽  
Guilherme F. Rosetti ◽  
André L. C. Fujarra ◽  
Kazuo Nishimoto ◽  
Allan C. Oliveira
Keyword(s):  
Experimental Study ◽  
Free Surface ◽  
Large Volume ◽  
Periodic Motion ◽  
Transverse Direction ◽  
Irregular Waves ◽  
Regular Waves ◽  
Sea State ◽  
Wave Effects ◽  
Induced Motion

Aiming to complete the results presented before by Gonçalves et al. (2011) – Experimental Study on Vortex-Induced Motions (VIM) of a Large-Volume Semi-Submersible Platform, OMAE2011, the present work brings new experimental results on VIM of a large-volume semi-submersible platform, particularly concerning its coexistence with waves in the free surface. The VIM tests were performed in the presence of three regular waves and also three different conditions of sea state. According to the results, considerable differences between the presence of regular or irregular waves were observed. The motion amplitudes in the transverse direction decreased harshly when the regular waves were performed and no VIM was observed. In the case of sea state condition tests, the amplitudes decreased slightly but a periodic motion characterized by the VIM was observed. The results herein presented concern transverse and yaw motion amplitudes, as well as spectral analyses.

Hydrodynamic characteristics of vertical and quadrant face pile supported breakwater under oblique waves

2021 ◽  
pp. 147509022110313
Author(s):  
T J Jemi Jeya ◽  
V Sriram ◽  
V Sundar
Keyword(s):  
Experimental Study ◽  
Hydrodynamic Performance ◽  
Hydrodynamic Characteristics ◽  
Scattering Parameter ◽  
Oblique Waves ◽  
Test Conditions ◽  
Relative Water ◽  
Identical Test ◽  
Run Up ◽  
Water Depths

This paper presents the results from a comprehensive experimental study on the Quadrant Face Pile Supported Breakwater (QPSB) in two different water depths exposed to three different oblique wave attacks. The results are compared with that for a Vertical face Pile Supported Breakwater (VPSB) for identical test conditions. The paper compares the reflection coefficient, transmission coefficient, energy loss coefficient, non-dimensional pressure, and non-dimensional run-up as a function of the relative water depth and scattering parameter. The results obtained for QPSB are validated with existing results. The salient observations show that QPSB experiences better hydrodynamic performance characteristics than the VPSB under oblique waves.

Guidelines for CFD Simulations of Spar VIM

2013 ◽  
Author(s):  
Charles Lefevre ◽  
Yiannis Constantinides ◽  
Jang Whan Kim ◽  
Mike Henneke ◽  
Robert Gordon ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Test Data ◽  
Model Test ◽  
Model Tests ◽  
Full Scale ◽  
Mooring System ◽  
Time Step ◽  
Cfd Simulations ◽  
Scaled Model ◽  
Sway Motion

Vortex-Induced Motion (VIM), which occurs as a consequence of exposure to strong current such as Loop Current eddies in the Gulf of Mexico, is one of the critical factors in the design of the mooring and riser systems for deepwater offshore structures such as Spars and multi-column Deep Draft Floaters (DDFs). The VIM response can have a significant impact on the fatigue life of mooring and riser components. In particular, Steel Catenary Risers (SCRs) suspended from the floater can be sensitive to VIM-induced fatigue at their mudline touchdown points. Industry currently relies on scaled model testing to determine VIM for design. However, scaled model tests are limited in their ability to represent VIM for the full scale structure since they are generally not able to represent the full scale Reynolds number and also cannot fully represent waves effects, nonlinear mooring system behavior or sheared and unsteady currents. The use of Computational Fluid Dynamics (CFD) to simulate VIM can more realistically represent the full scale Reynolds number, waves effects, mooring system, and ocean currents than scaled physical model tests. This paper describes a set of VIM CFD simulations for a Spar hard tank with appurtenances and their comparison against a high quality scaled model test. The test data showed considerable sensitivity to heading angle relative to the incident flow as well as to reduced velocity. The simulated VIM-induced sway motion was compared against the model test data for different reduced velocities (Vm) and Spar headings. Agreement between CFD and model test VIM-induced sway motion was within 9% over the full range of Vm and headings. Use of the Improved Delayed Detached Eddy Simulation (IDDES, Shur et al 2008) turbulence model gives the best agreement with the model test measurements. Guidelines are provided for meshing and time step/solver setting selection.

scholarly journals Toward improved heat dissipation of the turbulent regime over backward-facing step for the AL2O3-water nanofluids: An experimental approach

2019 ◽  
Vol 23 (3 Part B) ◽  
pp. 1779-1789 ◽  
Author(s):  
Syed Ahmed ◽  
Salim Kazi ◽  
Ghulamullah Khan ◽  
Mohd Zubir ◽  
Mahidzal Dahari ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Turbulent Regime ◽  
Al2o3 Nanoparticles ◽  
Backward Facing Step ◽  
Constant Weight ◽  
Weight Concentration

Experimental study of nanofluid flow and heat transfer to fully developed turbulent forced convection flow in a uniformly heated tubular horizontal backward-facing step has reported in the present study. To study the forced convective heat transfer coefficient in the turbulent regime, an experimental study is performed at a different weight concentration of Al2O3 nanoparticles. The experiment had conducted for water and Al2O3 -water nanofluid for the concentration range of 0 to 0.1 wt.% and Reynolds number of 4000 to 16000. The average heat transfer coefficient ratio increases significantly as Reynolds number increasing, increased from 9.6% at Reynolds number of 4000 to 26.3% at Reynolds number of 16000 at the constant weight concentration of 0.1%. The Al2O3 water nanofluid exhibited excellent thermal performance in the tube with a backwardfacing step in comparison to distilled water. However, the pressure losses increased with the increase of the Reynolds number and/or the weight concentrations, but the enhancement rates were insignificant.

An Experimental Study of the Viscous Resistance of a 0,564-CB Form

1979 ◽  
Vol 23 (02) ◽  
pp. 140-156
Author(s):  
P. N. Joubert ◽  
P. H. Hoffmann
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Skin Friction ◽  
Resistance Coefficient ◽  
Viscous Resistance ◽  
Local Skin ◽  
Friction Resistance ◽  
Local Skin Friction ◽  
The University ◽  
Resistance Coefficients

Wind tunnel tests were performed to determine the viscous resistance and its components for a 0.564-CB model from the BSRA Trawler Series. It was found that the sum of the pressure and skin friction resistance coefficients agreed well with the viscous resistance coefficient determined from drag balance tests. The range of Reynolds number examined was from 1.15 × 106 to 5.17 × 106. The results for the viscous resistance and its components were fitted using least-squares methods to various equations. The results were also compared with the results of previous tests done at the University of Melbourne on models of Lucy Ash-. ton and a 0.80-CB tanker. It was found that the skin friction and viscous resistance coefficients had curves of quite different position and slope. Local skin friction distribution showed noteworthy differences, especially at the stern, with high values at the keel and low values approaching the waterline.

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