On Roll Hydrodynamics of FPSO’s Fitted With Bilge Keels and Riser Balcony

2011 ◽  
Author(s):  
R. van ’t Veer ◽  
F. Fathi ◽  
J. G. Kherian
Keyword(s):  
Model Test ◽  
Potential Flow ◽  
Model Tests ◽  
Continuous Operation ◽  
Motion Prediction ◽  
Roll Motion ◽  
Test Results ◽  
Site Location ◽  
Cfd Simulations ◽  
Roll Damping

The topic of this paper is the roll motion prediction of ship-shaped FPSO’s, designed for continuous operation at site location. The maximum roll amplitude is a critical operability parameter which is difficult to predict accurately due to the nonlinear roll damping associated with the appendages. This paper contributes to the understanding of roll damping physics through model test results, CFD simulations and potential flow predictions. The model tests discussed concern two different Floating Production, Storage and Offloading (FPSO) units, designed by SBM as spread-moored units for operation offshore Brazil. The relevant roll damping appendages are the bilge keels on both sides and the submerged riser balcony on one side of the vessel. In particular the riser balcony complicates the motion prediction and was a main reason for the model tests and CFD investigation. The results presented focus on roll motion prediction in the frequency domain.

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.

Development and Verification of Modeling Practice for CFD Decay Calculations to Obtain Roll Damping of FPSO

2021 ◽  
Author(s):  
Arjen Koop ◽  
Pierre Crepier ◽  
Sebastien Loubeyre ◽  
Corentin Dobral ◽  
Kai Yu ◽  
...  
Keyword(s):  
Model Test ◽  
Test Results ◽  
Cfd Modelling ◽  
Roll Damping ◽  
Natural Period ◽  
Computational Mesh ◽  
Safety Studies ◽  
Offshore Industry ◽  
Decay Tests ◽  
Set Up

Abstract Estimates for roll damping are important input parameters for simulation studies on vessels operating at sea, e.g. FPSO mooring in waves, wind and current, workability and operability investigations, Dynamic Position studies, ship-to-ship operations and safety studies of vessels. To accurately predict the motions of vessels this quantity should be determined with confidence in the values. Traditionally, model experiments in water basins using so-called decay tests are carried out to determine the roll damping. With recent advancements in CFD modelling, the offshore industry has started using CFD as an alternative tool to compute the roll damping of FPSO’s. In order to help adopt CFD as a widely accepted tool, there is a need to develop confidence in CFD predictions. Therefore, a practical CFD modelling practice is developed within the Reproducible CFD JIP for roll decay CFD simulations. The Modelling Practice describes the geometry modelling, computational mesh, model set-up and post-processing for these type of CFD calculations. This modelling practice is verified and validated by three independent verifiers against available model test data. This paper provides an overview of the developed modelling practice and the calculated CFD results from the verifiers. The CFD modelling practice is benchmarked against available model test results for a tanker-shaped FPSO. By following this modelling practice, the CFD predictions for the equivalent linear damping coefficient and natural period of the roll motions are within 10% for all verifiers and within 10% from the model test results. Therefore, we conclude that when following the developed modelling practice for roll decay simulations, reliable, accurate and reproducible results can be obtained for the roll damping of tanker-shaped FPSOs.

Experimental Study on the Influence of Appendages on a Yacht Rolling at Zero Froude Number

2004 ◽  
Vol 41 (04) ◽  
pp. 200-206
Author(s):  
Kim Klaka ◽  
Martin Renilson
Keyword(s):  
Experimental Study ◽  
Froude Number ◽  
Model Test ◽  
Roll Motion ◽  
Forward Speed ◽  
Test Results

Yachts tend to roll uncomfortably while at anchor, causing discomfort to the crew and passengers, generating additional stresses on equipment, and making such operations as embarking and disembarking hazardous activities. Currently, there is a dearth of data regarding roll motions at zero forward speed for hull shapes dominated by large appendages. Hence, an experimental study into the effect of large appendages on roll motion was undertaken. The model test results are presented, showing how changes in appendage geometry alter the roll response.

Improved Strake Design for Vortex Induced Motions of Spar Platforms

2005 ◽  
Author(s):  
Mehernosh Irani ◽  
Lyle Finn
Keyword(s):  
Model Test ◽  
Model Tests ◽  
Test Results ◽  
Test Program ◽  
Test Set ◽  
Test Methodology ◽  
Spar Platforms ◽  
Truss Spar ◽  
Set Up

An extensive model test program was conducted to explore the effectiveness of alternate strake designs to reduce Truss Spar VIV response. Different strake configurations were tested to minimize VIV response. The paper presents results of the model tests. The model test set-up is described, important parameters that are modeled (including hull and truss geometry, strake configuration, mass and mooring properties) and considerations of instrumentation and test methodology are discussed. The paper also describes the analysis of the test results and shows the effectiveness of new strake design. The present results are compared with VIV response of existing Truss Spars with conventional strake design.

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.

scholarly journals Model-Scale/Full-Scale Correlation of NRC-OCRE’s Model Resistance, Propulsion and Maneuvering Test Results

2015 ◽  
Author(s):  
Michael Lau
Keyword(s):  
Test Data ◽  
Model Test ◽  
Model Tests ◽  
Full Scale ◽  
Test Results ◽  
Sea Trial ◽  
Model Scale ◽  
Performance Predictions ◽  
Ice Strength ◽  
Scale Data

There are a variety of model ices and test techniques adopted by model test facilities. Most often, the clients would ask: “How well can you predict the full scale performance from your model test results?” Model-scale/full-scale correlation becomes an important litmus test to validate a model test technique and its results. This paper summarizes the model-scale/full-scale correlation performed on model test data generated at the National Research Council - Ocean, Coastal, and River Engineering’s (NRC-OCRE) test facility in St. John’s. This correlation includes ship performance predictions, i.e., resistance, propulsion and maneuvering. Selected works from NRC-OCRE on the USCGC icebreaker Healy, the CCGS icebreaker Terry-Fox, the CCGS R-Class icebreakers Pierre Radisson and Sir John Franklin and the CCGS icebreaker Louis S. St. Laurent were reviewed and summarized. The model tests were conducted at NRC-OCRE’s ice tank with the correct density (CD) EGADS model ice. This correlation is based on the concept that a “correlation friction coefficient” (CFC) can be used to predict full-scale ship icebreaking resistance from model test data. The CFCs have been compared for correlation studies using good-quality full-scale information for the five icebreaker models in the NRC-OCRE’s model test database. The review has shown a good agreement between NRCOCRE’s model test predictions and full-scale measurements. The resistance and power correlation were performed for five sets of full-scale data. Although there is substantial uncertainty on ice thickness and ice strength within the full scale data sets that contributes to data scattering, the data suggest a conservative estimate can be obtained to address reasonably this uncertainty by increasing the model prediction by 15% that envelopes most data points. Limited correlation for maneuvering in ice was performed for the USCGC icebreaker Healy. Selected test conditions from the sea trials were duplicated for the maneuvering tests and turning diameters were measured from the arcs of partial circles made in the ice tank. Performance predictions were then compared to the full-scale data previously collected. Despite some discrepancy in ice strength and power level between the model tests and sea trial, the model data agree well with the sea trial data except for three outliers. Otherwise, the maneuvering data show a good correlation between the model test and sea trial results.

On the Sensitivity of the Roll Motion of an FPSO

2002 ◽  
Author(s):  
Martijn H. J. Kragtwijk ◽  
Tone M. Vestbo̸stad ◽  
Jan H. Vugts ◽  
Ove T. Gudmestad
Keyword(s):  
Theoretical Model ◽  
Potential Theory ◽  
Computer Programs ◽  
Model Tests ◽  
Full Scale ◽  
Roll Motion ◽  
Linear Potential ◽  
Roll Damping ◽  
Linear Potential Theory

This paper describes a theoretical model that has been used to investigate the roll motion of an FPSO. The Statoil operated Norne FPSO at Haltenbanken off central Norway has been used as a reference for the investigation. The model is based on linear potential theory. The viscous roll damping has been incorporated by linearizing the effect. Problems when simultaneously using various computer programs, textbooks and the theoretical model are highlighted. Also areas of caution when working with model tests are identified. The theoretical model has been used to investigate the sensitivity of the roll motion to certain key parameters. The theoretical model has further been compared with results from model tests and with full-scale measurements. The results of these comparisons are described and conclusions and recommendations following the investigation are presented.

Model Test Data Correlations With Fully Coupled Hull/Mooring Analysis for a Floating Wind Turbine on a Semi-Submersible Platform

2014 ◽  
Author(s):  
Bonjun Koo ◽  
Andrew J. Goupee ◽  
Kostas Lambrakos ◽  
Ho-Joon Lim
Keyword(s):  
Wind Turbine ◽  
Model Test ◽  
Model Tests ◽  
Test Results ◽  
Scaled Model ◽  
Floating Wind Turbine ◽  
Mooring Dynamics ◽  
Set Up ◽  
Fully Coupled ◽  
Turbine Model

The DeepCwind floating wind turbine model tests were performed at MARIN (Maritime Research Institute Netherlands) with a model set-up corresponding to a 1:50 Froude scaling. In the model tests, the wind turbine was a scaled model of the National Renewable Energy Lab (NREL) 5MW, horizontal axis reference wind turbine supported by three different generic floating platforms: a spar, a semi-submersible and a tension-leg platform (TLP) (Ref. [1] and [2]). This paper presents validation of the MLTSIM-FAST [3] code with DeepCwind semi-submersible wind turbine model test results. In this integrated program, the turbine tower and rotor dynamics are simulated by the subroutines of FAST [4], and the hydrodynamic loads and mooring system dynamics are simulated by the subroutines of MLTSIM. In this study, fully coupled hull/mooring dynamics and second-order difference-frequency response are included in MLTSIM-FAST. The analysis results are systematically compared with model test results and show good agreement.

Bearing capacity of foundations on a weak sand layer overlying a strong deposit

1982 ◽  
Vol 19 (3) ◽  
pp. 392-396 ◽  
Author(s):  
A. M. Hanna
Keyword(s):  
Bearing Capacity ◽  
Model Test ◽  
Classical Equation ◽  
Model Tests ◽  
Sand Layer ◽  
Test Results ◽  
Dense Sand ◽  
Design Charts ◽  
Sand Deposit ◽  
Compact Sand

The ultimate bearing capacity of footings resting on subsoils consisting of a weak sand layer overlying a strong deposit has been investigated. Based on model tests of strip and circular footings in a loose or compact sand layer overlying a dense sand deposit, the classical equation of bearing capacity of footings on homogeneous sand was extended to cover cases of these footings in layered sands where the upper layer is the weaker. The theory compared well with the available model test results. Design charts are presented.

Research on Longitudinal Motion Prediction of Hybrid Monohull Considering Based on Numerical Simulation

2014 ◽  
Vol 716-717 ◽  
pp. 776-779
Author(s):  
Bo Tian ◽  
Hui Long Ren ◽  
Zhi Yuan Dong
Keyword(s):  
Numerical Simulation ◽  
Model Test ◽  
Potential Flow ◽  
Motion Prediction ◽  
Longitudinal Motion ◽  
Hydrodynamic Coefficients ◽  
Regular Waves ◽  
Damping Force ◽  
Main Component ◽  
Rans Method

The shape of hybrid monohull at the bow is quite complex and the viscosity force is the main component of the damping force in the drainage area of the bow when the ship moves in waves so that the result of the motion predicition by the traditional potential flow method is very different from the result of experiments. This paper tries to use new numerical compute method considering the effect of the viscosity to improve the precision of the sea keeping predicition. Based on the Reynolds Averaged N-S Equations (RANS) method, the paper takes a hrbrid monohull to compute the hydrodynamic coefficients. According to the result of model test, the prediction of the hybrid monohull’s the longitudinal motion in regular waves at speed of 18kn also indicates that RANS method can reflect viscid influence reducing the motion of hybrid monohull in waves.

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