Performance Simulation of a Dual-Direction Ship in Level Ice

2014 ◽  
Vol 58 (03) ◽  
pp. 168-181
Author(s):  
Xiang Tang ◽  
Kaj Riska ◽  
Torgeir Moan
Keyword(s):  
Test Data ◽  
Model Test ◽  
Performance Prediction ◽  
Numerical Procedure ◽  
Model Tests ◽  
Prediction Tool ◽  
Continuous Mode ◽  
Performance Simulation ◽  
Level Ice ◽  
A Performance

The ice performance of a dual-direction ship is investigated through a numerical procedure developed to simulate the continuous-mode icebreaking in level ice. The effect of the propeller-hull-ice interaction for running astern is accounted for by applying the knowledge obtained from model tests to the numerical procedure. The numerical procedure is in turn used as a performance prediction tool to supplement the model test data to investigate the thrust deduction in ice.

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.

Numerical Investigation for Vortex-Induced Vibrations of Steel-Lazy-Wave-Risers: Part I — CFD Validation Against Forced Oscillation Model Test

2019 ◽  
Author(s):  
Hyunchul Jang ◽  
Jang Whan Kim
Keyword(s):  
Test Data ◽  
Model Test ◽  
Cfd Simulation ◽  
Assessment Tool ◽  
Forced Oscillation ◽  
Model Tests ◽  
Hydrodynamic Coefficients ◽  
Cfd Validation ◽  
Oscillation Model ◽  
Water Developments

Abstract Vortex-Induced Vibration (VIV) is one of the main sources of fatigue damage for long slender risers. Typical VIV assessment of risers is conducted using semi-empirical software tools with the sectional hydrodynamic coefficients derived from forced-oscillation model tests on short rigid riser sections. The Steel Lazy Wave Riser (SLWR) with buoyancy sections is an attractive concept for improving fatigue performance in deep water developments, but there is limited model test data available for the hydrodynamic coefficients on SLWR’s. CFD simulation is an alternative VIV assessment tool, once it is validated for an existing model test. It can provide accurate estimates of VIV response and help to design configurations of SLWR’s without additional model tests. The present CFD simulations are performed to validate hydrodynamic coefficients of a SLWR section. The predicted drag and excitation (lift) coefficients on both bare riser and buoyancy sections are compared to the test data with respect to oscillation frequency and amplitude.

Benchmark Study Between CFD and Model Tests on a Semi-Submersible Crane Vessel

2009 ◽  
Author(s):  
Harald Ottens ◽  
Radboud van Dijk ◽  
Geert Meskers
Keyword(s):  
Test Data ◽  
Model Test ◽  
Offshore Structures ◽  
Model Tests ◽  
Lessons Learned ◽  
Data Sets ◽  
General Acceptance ◽  
Heavy Lift ◽  
Semi Empirical ◽  
Proven Method

Accurate assessment of current loads on offshore vessels is required to determine operability of heavy lift and pipe lay operations. Whereas in the past only semi-empirical methods or model tests were suitable to obtain these data, CFD has recently become available as engineering tool to assess current loads on offshore structures. CFD has the potential to assess current loads more flexible in a numerical manner. Although the application of CFD has proven its value in assessment of ships resistance and VIV calculations, CFD is still not yet a fully proven method to calculate the current loads on offshore structures. Therefore validation of the results is further required to reach general acceptance of this method for offshore applications. HMC took the initiative to compare and validate CFD results with its model test data of current loads on one of its semi-submersible crane vessels. In this paper a comparison of CFD results with model test data of the current loads of a semi-submersible crane vessel is presented. The CFD calculations are performed as blind computations, so the model tests results were unknown. Afterwards the CFD results are compared with the results of the model tests. Based on both data sets lessons learned are addressed to improve the CFD computations as well as practical aspects and limitations of current load model testing. Furthermore, the possibilities to use CFD to scale the results of the model tests to full scale are explored. Based on this comparison CFD appears to be a complementary, flexible and reliable tool in assessing the current loads on mission critical vessel operations.

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.

scholarly journals Validation of Numerical Wave Tank Simulations Using REEF3D With JONSWAP Spectra in Intermediate Water Depth

2020 ◽  
Author(s):  
Csaba Pakozdi ◽  
Sebastien Fouques ◽  
Maxime Thys ◽  
Arun Kamath ◽  
Weizhi Wang ◽  
...  
Keyword(s):  
Test Data ◽  
Model Test ◽  
Water Depth ◽  
Model Tests ◽  
Irregular Waves ◽  
Wave Crest ◽  
Intermediate Water ◽  
Numerical Wave Tank ◽  
Wave Tank ◽  
Numerical Wave

Abstract As offshore wind turbines increase in size and output, the support structures are also growing. More sophisticated assessment of the hydrodynamic loads is needed, particularly for the ultimate limit state design. For higher-order phenomena related to rare steep wave events such as ringing, a better understanding of the stochastic loads is needed. As an innovative step forward to reduce the cost of extensive model tests with irregular waves, a larger number of investigations can be carried out using high-performance high-fidelity numerical simulations after an initial stochastic validation with model test data. In this paper, the open-source hydrodynamic model REEF3D::FNPF (Fully Nonlinear Potential Flow) is used to carry out three-hour long simulations with the JONSWAP spectrum in intermediate water depth conditions. Statistical properties of the free surface elevation in the numerical wave tank are validated using the available data from model tests carried out at SINTEF Ocean/NTNU. The spectral shape, significant wave height, peak period, skewness, kurtosis, and wave crest height statistics are compared. The results are analyzed and it is found that the numerical model provides reasonably good agreement with the model test data.

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