Full Scale CFD Validation on Thruster-Hull Interaction on a Semi-Submersible Crane Vessel in Transit Condition

2013 ◽  
Author(s):  
Harald Ottens ◽  
Norbert Bulten ◽  
Radboud van Dijk
Keyword(s):  
Test Data ◽  
Model Test ◽  
Life Time ◽  
Full Scale ◽  
Cfd Simulations ◽  
Cfd Validation ◽  
Lessons Learnt ◽  
Thrust Efficiency ◽  
In Transit ◽  
Scale Data

Heerema Marine Contractors operates three semi-submersible crane vessels; the Thialf, Balder and Hermod. The first two vessels are equipped with a DP system. The ability of each crane vessel to keep its position depends highly on the performance of the DP system of that crane vessel. The thrust efficiency of the DP system depends on the efficiency of the individual thruster, but also on the interaction of the thruster wake and the hull of the vessel. Thruster-hull interaction is important during operations, but also during transits from one location to another. During the transits of the Balder and Thialf, the DP thrusters are used as propulsion. Understanding the thruster-hull interaction effects in this transit condition can result in an optimum thrust setting. In previous validation studies CFD was used to assess the current loads and the thruster-hull interaction on a semi-submersible vessel. In these studies the CFD results were validated with a series of dedicated model tests. The comparison between the CFD and model test data shows that CFD is able to predict the relevant force components within a sufficient accuracy for engineering purposes. However, Heerema Marine Contractors is mainly interested in full scale data. Unfortunately, not much full scale data is available to validate the extrapolation of model test and CFD results to full scale thruster efficiency. Therefore a first validation study is performed based on acquired full scale data during a transit of the Thialf in Q4 2011. Comparing the full scale test data with the CFD results shows that the CFD can be used to predict which settings is the most efficient. Optimization of thruster settings on semi-submersible vessels is not trivial due to number and location of the azimuth thrusters. Using CFD simulations the power settings and azimuth angles of the thrusters were changed to obtain the optimal thrust setting during transit. In Q2 2012 the Thialf made her first transit after a dry-dock period in which the hull was cleaned and painted. Repeating similar tests conditions as in Q4 2011 demonstrates the effect of a clean hull. Additional tests demonstrated the effect of a more efficient thrust setting originated by the CFD results. The implications of the optimized azimuth setting in transit on the life time of the thruster is verified using CFD and FEM. The paper addresses lessons learnt to improve the CFD simulations as well as practical aspects and limitations of thrust efficiency modeling using CFD. It demonstrates that CFD can be used to understand the associated flow physics and that CFD can be used to predict improvements in thrust efficiencies. In addition, some lessons learnt on full scale monitoring will be addressed.

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 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.

Benchmark Study on Thruster-Hull Interaction in Current on a Semi-Submersible Crane Vessel

2012 ◽  
Author(s):  
Harald Ottens ◽  
Radboud van Dijk
Keyword(s):  
Test Data ◽  
Model Test ◽  
Numerical Study ◽  
Numerical Data ◽  
Model Tests ◽  
Full Scale ◽  
Model Scale ◽  
Thrust Efficiency ◽  
Force Components ◽  
The Individual

The ability of a DP-vessel to keep its position depends highly on the performance of the DP system. The thrust efficiency of the DP-system depends on the efficiency of the individual thrusters, but also on the interaction of the thruster wake and the hull of the vessel. This thruster-hull interaction becomes even more important when the vessel is a semi-submersible vessel; the thruster wake of the thruster on the upstream pontoon might impinge on the downstream pontoon resulting in high losses in efficiency and reduced DP-capability. Heerema Marine Contractors has two DP-semi-submersible crane vessels; the Thialf and Balder. An assessment of the thrust efficiency of the DP thrusters of these vessels has been made by comparing CFD computations with dedicated model tests. In previous benchmark studies CFD is used to assess the current loads as well as thruster-hull interaction without current on a semi-submersible vessel. The logical next step is to perform a numerical study on a thruster-hull interaction with current. Similar as the previous benchmark studies the numerical data are validated with a series of dedicated model tests. The model test data include the global forces, the forces on each individual pontoon and the forces of each individual thruster, including the nozzle thrust and propeller thrust. The comparison between the CFD and model test data shows that CFD is able to predict the relevant force components within a sufficient accuracy for engineering purposes. At present not much is known about the extrapolation of model scale DP-thrust efficiency to full scale DP-thrust efficiency, neither for model test results, nor for CFD results. Scaling CFD from model scale to full scale is not trivial; it involves a significant change in Reynolds number, a different description of boundary layer and poses challenges to meshing and grid. Therefore, validation is required. A first validation study is performed based on data acquired during a transit of SSCV Thialf in Q4 2011. In preparation, CFD simulations are performed for different thrust combinations. These results are compared to full scale observations and, where possible, improvements to the numerical modeling are assessed. The paper addresses lessons learnt to improve the CFD computations as well as practical aspects and limitations of thrust efficiency modeling, including all interaction effects, using CFD from an engineering perspective.

Observations on the Effect of Vessel Speed on Bow Thruster Performance

1971 ◽  
Vol 8 (01) ◽  
pp. 93-96
Author(s):  
Donald E. Ridley
Keyword(s):  
Test Data ◽  
Model Test ◽  
Full Scale ◽  
Scale Data ◽  
Vessel Speed

The paper explores the effect of vessel speed on thruster performance by comparing fullscale data to model test data. The steering effect of the thruster alone, and in combination with the rudder, is considered. A limited amount of full-scale data on the steering effect of a bow thruster, with the vessel proceeding astern, is presented.

scholarly journals Model Test of a 1:8-Scale Floating Wind Turbine Offshore in the Gulf of Maine1

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Anthony M. Viselli ◽  
Andrew J. Goupee ◽  
Habib J. Dagher
Keyword(s):  
Wind Turbine ◽  
Physical Model ◽  
Test Data ◽  
Model Test ◽  
Test Site ◽  
Full Scale ◽  
Scale Construction ◽  
Offshore Wind ◽  
Testing Effort ◽  
Floating Wind Turbine

A new floating wind turbine platform design called VolturnUS developed by the University of Maine uses innovations in materials, construction, and deployment technologies such as a concrete semisubmersible hull and a composite tower to reduce the costs of offshore wind. These novel characteristics require research and development prior to full-scale construction. This paper presents a unique offshore model testing effort aimed at derisking full-scale commercial projects by providing scaled global motion data, allowing for testing of materials representative of the full-scale system, and demonstrating full-scale construction and deployment methods. A 1:8-scale model of a 6 MW semisubmersible floating wind turbine was deployed offshore Castine, ME, in June 2013. The model includes a fully operational commercial 20 kW wind turbine and was the first grid-connected offshore wind turbine in the U.S. The testing effort includes careful selection of the offshore test site, the commercial wind turbine that produces the correct aerodynamic thrust given the wind conditions at the test site, scaling methods, model design, and construction. A suitable test site was identified that produced scaled design load cases (DLCs) prescribed by the American Bureau of Shipping (ABS) Guide for Building and Classing Floating Offshore Wind Turbines. A turbine with a small rotor diameter was selected because it produces the correct thrust load given the wind conditions at the test site. Some representative data from the test are provided in this paper. Model test data are compared directly to full-scale design predictions made using coupled aeroelastic/hydrodynamic software. Scaled VolturnUS performance data during DLCs show excellent agreement with full-scale predictive models. Model test data are also compared directly without scaling against a numerical representation of the 1:8-scale physical model for the purposes of numerical code validation. The numerical model results compare favorably with data collected from the physical model.

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.

Effect of Tunnel Entrance Configuration on Thruster Performance

1969 ◽  
Vol 6 (01) ◽  
pp. 60-65
Author(s):  
Donald E. Ridley
Keyword(s):  
Drag Coefficient ◽  
Test Data ◽  
Model Test ◽  
Full Scale ◽  
Full Scale Tests ◽  
Tunnel Entrance

The paper is concerned with the effect of tunnel entrance configuration on thrust produced and hull resistance augmentation. A means of determining equivalent fairing radius is presented, and model test data from two sources are correlated with a limited number of full-scale tests. A method of determining whether resistance will be increased by the addition of a thruster tunnel is postulated. This method is checked against one set of model test data with two thruster tunnels, one forward and one aft, from which a drag coefficient for faired entrance sections is derived.

Model Test of a 1:8 Scale Floating Wind Turbine Offshore in the Gulf of Maine

2014 ◽  
Author(s):  
Anthony M. Viselli ◽  
Andrew J. Goupee ◽  
Habib J. Dagher
Keyword(s):  
Wind Turbine ◽  
Physical Model ◽  
Test Data ◽  
Model Test ◽  
Test Site ◽  
Full Scale ◽  
Scale Construction ◽  
Offshore Wind ◽  
Testing Effort ◽  
Floating Wind Turbine

A new floating wind turbine platform design called VolturnUS developed by the University of Maine uses innovations in materials, construction, and deployment technologies such as a concrete semi-submersible hull and a composite tower to reduce the costs of offshore wind. These novel characteristics require research and development prior to full-scale construction. This paper presents a unique offshore model testing effort aimed at de-risking full-scale commercial projects by providing properly scaled global motion data, allowing for implementation of full-scale structural materials, and demonstrating full-scale construction and deployment methods. The model is a 1:8-scale model of a 6MW semi-submersible floating wind turbine and was deployed offshore Castine, Maine, USA in June, 2013. The model uses a fully operational turbine and was the first grid connected offshore wind turbine in the Americas. The testing effort includes careful treatment of the offshore test site, scaling methods, model design, and construction. A suitable test site was identified that provides the correct proportions of wind and wave loading in order to simulate design load cases prescribed by the American Bureau of Shipping Standard for Building and Classing Floating Offshore Wind Turbines. Sample model test data is provided. Model test data is directly compared to full-scale design predictions made using coupled aeroelastic/ hydrodynamic software. VolturnUS performance data from scaled extreme sea states show excellent agreement with predictive models. Model test data are also compared to a numerical representation of the physical model for the purposes of numerical code validation. The numerical model results compare very favorably with data collected from the physical model.

Component Approach for Confident Predications of Deepwater CALM Buoy Coupled Motions: Part 2 — Analytical Implementation

2005 ◽  
Author(s):  
M. J. Santala ◽  
Z. J. Huang ◽  
H. Wang ◽  
T. W. Yung ◽  
W. Kan ◽  
...  
Keyword(s):  
Test Data ◽  
Model Test ◽  
System Analysis ◽  
Line Tension ◽  
Analytical Tool ◽  
Full Scale ◽  
Hydrodynamic Coefficients ◽  
Model Scale ◽  
Oscillation Test ◽  
Component Approach

This paper describes an analytical implementation of the component approach for motion predictions of a deepwater CALM buoy as described in the companion paper “Component Approach for Confident Predictions of Deepwater CALM Buoy Coupled Motions — Part 1: Philosophy”. The implementation of the approach starts with a “model-of-the-model” validation of the analytical tool. Emphasis is given to making an accurate analytical characterization of the model as tested. To capture the strong coupling between the buoy motions and line dynamics the analyses described herein were carried out in the time-domain. This allows a rigorous treatment of the hydrodynamic forces on the buoy as well as the non-linear mooring loads when analyzing the buoy responses in waves. Since the validation analysis is a model-of-the-model practice at model scale, the proper application of the validated tool to the full-scale system is discussed. This involves modeling of the exact full-scale system and the proper selection of the hydrodynamic coefficients for the buoy and lines. In this paper we will present the numerical modeling procedures and the results from validation work to confirm that the analytical tool is validated correctly. Detailed results from validation analysis versus model test data will be shown for system components including buoy hydrodynamics from the forced oscillation test, line tension from line oscillation test, and the motions and tensions of integrated buoy/mooring/riser system. We point out that the hydrodynamic coefficients at model scale can not be directly applied to the full-scale system analysis even though they are from model test measurements. We will present the difference between the results of the model-scale system using model scale hydrodynamic coefficients and those based on a proper range of the coefficients at full-scale. This will highlight the need to design component tests to determine appropriate full scale coefficients in order to improve the accuracy of full-scale design predictions. These results will show the advantages of adopting a component approach over the common industry practices in the areas of correct use of model test data, validation analysis and the analysis of the coupled CALM buoy system responses in waves.

scholarly journals Estimation of Great Lakes Bulk Carrier Resistance Based on Model Test Data Regression

1973 ◽  
Vol 10 (04) ◽  
pp. 364-379
Author(s):  
Peter M. Swift ◽  
Horst Nowacki ◽  
Joseph P. Fischer
Keyword(s):  
Regression Analysis ◽  
Great Lakes ◽  
Test Data ◽  
Model Test ◽  
Full Scale ◽  
Bulk Carrier ◽  
Scale Resistance ◽  
Data Regression ◽  
Bulk Carriers

Tank data have been collected, analyzed, and standardized for 50 tests of Great Lakes bulk carriers. Regression analysis has been applied in order to estimate the coefficient of residuary resistance of such vessels in terms of their nondimensional form parameters. The results are presented for Froude numbers from 0.11 to 0.18 in the form of coefficients obtained by three different regressions, and in the form of charts at Froude numbers 0.14 and 0.16. Examples illustrate the use of the regression formulas in estimating the full-scale resistance.

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