Global Analysis of a Floating Wind Turbine Using an Aero-Hydro-Elastic Numerical Model: Part 2—Benchmark Study

2011 ◽  
Author(s):  
Neil Luxcey ◽  
Harald Ormberg ◽  
Elizabeth Passano
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Global Analysis ◽  
Weather Conditions ◽  
Irregular Waves ◽  
Benchmark Study ◽  
Floating Wind Turbine ◽  
Calm Water ◽  
Internal Forces ◽  
System Power

This paper describes and presents the results of a benchmark study of a floating wind turbine numerical model that includes aero- and hydro-elasticity. The modelled wind turbine is the NREL offshore 5 MW baseline wind turbine whose specifications are publicly available. The first part of this paper demonstrates the importance of including aeroelasticity and hydroelasticity in the system. Power production, internal forces and motion amplitudes are compared to results from models using a rigid tower and rigid blades. Comparisons are performed for different weather conditions such as calm water, regular and irregular waves, constant and varying wind. The consequences of including elasticity in the different parts of the model are studied. The second part of the paper presents a benchmark study against the codes of the Offshore Code Comparison Collaboration. The floater motions, blade and tower deflection and power generation are presented and discussed.

Calibration of a Time-Domain Hydrodynamic Model for A 12 MW Semi-Submersible Floating Wind Turbine

2021 ◽  
Author(s):  
Carlos Eduardo Silva de Souza ◽  
Nuno Fonseca ◽  
Petter Andreas Berthelsen ◽  
Maxime Thys
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Time Domain ◽  
Quadratic Model ◽  
Wave Loads ◽  
Frequency Wave ◽  
Load Models ◽  
Wave Drift ◽  
Floating Wind Turbine ◽  
Decay Tests

Abstract Design optimization of mooring systems is an important step towards the reduction of costs for the floating wind turbine (FWT) industry. Accurate prediction of slowly-varying horizontal motions is needed, but there are still questions regarding the most adequate models for low-frequency wave excitation, and damping, for typical FWT concepts. To fill this gap, it is fundamental to compare existing load models against model tests results. This paper describes a calibration procedure for a three-columns semi-submersible FWT, based on adjustment of a time-domain numerical model to experimental results in decay tests, and tests in waves. First, the numerical model and underlying assumptions are introduced. The model is then validated against experimental data, such that the adequate load models are chosen and adjusted. In this step, Newman’s approximation is adopted for the second-order wave loads, using wave drift coefficients obtained from the experiments. Calm-water viscous damping is represented as a linear and quadratic model, and adjusted based on decay tests. Additional damping from waves is then adjusted for each sea state, consisting of a combination of a wave drift damping component, and one component with viscous nature. Finally, a parameterization procedure is proposed for generalizing the results to sea states not considered in the tests.

Hybrid Scaled Testing of a 5MW Floating Wind Turbine Using the SiL Method Compared With Numerical Models

2018 ◽  
Author(s):  
Felipe Vittori ◽  
Faisal Bouchotrouch ◽  
Frank Lemmer ◽  
José Azcona
Keyword(s):  
Wind Turbine ◽  
Numerical Models ◽  
Hydrodynamic Forces ◽  
Irregular Waves ◽  
Mooring Line ◽  
Global Dynamics ◽  
Aerodynamic Forces ◽  
Wave Tank ◽  
Aerodynamic Damping ◽  
Floating Wind Turbine

The design of floating wind turbines requires both, simulation tools and scaled testing methods, accurately integrating the different phenomena involved in the system dynamics, such as the aerodynamic and hydrodynamic forces, the mooring lines dynamics and the control strategies. In particular, one of the technical challenges when testing a scaled floating wind turbine in a wave tank is the proper integration of the rotor aerodynamic thrust. The scaling of the model based on the Froude number produces equivalent hydrodynamic forces, but out of scale aerodynamic forces at the rotor, because the Reynolds number, that governs the aerodynamic forces, is not kept constant. Several approaches have been taken to solve this conflict, like using a tuned drag disk or redesigning the scaled rotor to provide the correct scaled thrust at low Reynolds numbers. This work proposes a hybrid method for the integration of the aerodynamic thrust during the scaled tests. The work also explores the agreement between the experimental measurements and the simulation results through the calibration and improvement of the numerical models. CENER has developed a hybrid testing method that replaces the rotor by a ducted fan at the model tower top. The fan can introduce a variable force which represents the total wind thrust by the rotor. This load is obtained from an aerodynamic simulation that is performed in synchrony with the test and it is fed in real time with the displacements of the platform provided by the acquisition system. Thus, the simulation considers the displacements of the turbine within the wind field and the relative wind speed on the rotor, including the effect of the aerodynamic damping on the tests. The method has been called “Software-in-the-Loop” (SiL). The method has been applied on a test campaign at the Ecole Centrale de Nantes wave tank of the OC4 semisubmersible 5MW wind turbine, with a scale factor of 1/45. The experimental results have been compared with equivalent numerical simulations of the floating wind turbine using the integrated code FAST. Simple cases as only steady wind and free decays with constant wind showed a good agreement with computations, demonstrating that the SiL method is able to successfully introduce the rotor scaled thrust and the effect of the aerodynamic damping on the global dynamics. Cases with turbulent wind and irregular waves showed better agreement with the simulations when mooring line dynamics and second order effects were included in the numerical models.

Dynamic Modelling of a Spar Buoy Wind Turbine

2017 ◽  
Author(s):  
Giuseppe Roberto Tomasicchio ◽  
Alberto Maria Avossa ◽  
Luigia Riefolo ◽  
Francesco Ricciardelli ◽  
Elena Musci ◽  
...  
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Dynamic Modelling ◽  
Irregular Waves ◽  
Induced Response ◽  
Simulation Tool ◽  
Floating Structure ◽  
Mooring Lines ◽  
Wave Basin ◽  
Fast Wind

In the present paper, the dynamic response of a spar buoy wind turbine under different wind and wave conditions is discussed. Physical model tests were performed at the Danish Hydraulic Institute (DHI) off-shore wave basin within the EU-Hydralab IV Integrated Infrastructure Initiative. The OC3-Hywind spar buoy was taken as reference prototype. A spar buoy model, 1:40 Froude-scaled, was tested using long crested regular and irregular waves, orthogonal (0 degrees) and oblique (20 degrees) to the structure. Here the results concerning regular waves, with incidence orthogonal to the structure, are presented; the selected tests considered rotating and non-rotating blades. Measurements of displacements, rotations, accelerations, forces response of the floating structure and at the mooring lines were carried out. Based on the observed data, FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy’s (DOE’s), National Renewable Energy Laboratory (NREL), was calibrated and verified. The numerical model takes into account the wave induced response and the effects of the mooring lines on the overall system. The adopted spar buoy has three equally spaced mooring lines that were modelled as quasi-static taut or catenary lines through MAP++ (static module) and MoorDyn (dynamic module) in the FAST simulation tool. The tensions along the fairleads of the three mooring lines were examined. At the end of the calibration procedure, the numerical model was successfully used to simulate the dynamic motions of the floating wind turbine under combinations of wind and sea states for the selected wave attacks. All data from the DHI tests were converted to full scale using Froude scaling before being analyzed.

scholarly journals Proposal of a Novel Mooring System Using Three-Bifurcated Mooring Lines for Spar-Type Off-Shore Wind Turbines

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8303
Author(s):  
Shi Liu ◽  
Yi Yang ◽  
Chengyuan Wang ◽  
Yuangang Tu ◽  
Zhenqing Liu
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Line Length ◽  
Torsional Stiffness ◽  
Irregular Waves ◽  
Mooring Line ◽  
Mooring System ◽  
The Novel ◽  
Mooring Lines ◽  
Floating Wind Turbine

Floating wind turbine vibration controlling becomes more and more important with the increase in wind turbine size. Thus, a novel three-bifurcated mooring system is proposed for Spar-type floating wind turbines. Compared with the original mooring system using three mooring lines, three-bifurcated sub-mooring-lines are added into the novel mooring system. Specifically, each three-bifurcated sub-mooring-line is first connected to a Spar-type platform using three fairleads, then it is connected to the anchor using the main mooring line. Six fairleads are involved in the proposed mooring system, theoretically resulting in larger overturning and torsional stiffness. For further improvement, a clump mass is attached onto the main mooring lines of the proposed mooring system. The wind turbine surge, pitch, and yaw movements under regular and irregular waves are calculated to quantitatively examine the mooring system performances. A recommended configuration for the proposed mooring system is presented: the three-bifurcated sub-mooring-line and main mooring line lengths should be (0.0166, 0.0111, 0.0166) and 0.9723 times the total mooring line length in the traditional mooring system. The proposed mooring system can at most reduce the wind turbine surge movement 37.15% and 54.5% when under regular and irregular waves, respectively, and can at most reduce the yaw movement 30.1% and 40% when under regular and irregular waves, respectively.

scholarly journals On Tower Top Axial Acceleration and Drivetrain Responses in a Spar-Type Floating Wind Turbine

2017 ◽  
Author(s):  
Amir Rasekhi Nejad ◽  
Erin E. Bachynski ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Global Analysis ◽  
Correlation Study ◽  
Analysis Tool ◽  
Maximum Acceleration ◽  
Peak Period ◽  
Floating Wind Turbine ◽  
Axial Acceleration ◽  
Northern North Sea ◽  
Wave Induced

Common industrial practice for designing floating wind turbines is to set an operational limit for the tower-top axial acceleration, normally in the range of 0.2–0.3g, which is typically understood to be related to the safety of turbine components. This paper investigates the rationality of the tower-top acceleration limit by evaluating the correlation between acceleration and drivetrain responses. A 5 MW reference drivetrain is selected and modelled on a spar-type floating wind turbine in 320 m water depth. A range of environmental conditions are selected based on the long-term distribution of wind speed, significant wave height, and peak period from hindcast data for the Northern North Sea. For each condition, global analysis using an aero-hydro-servo-elastic tool is carried out for six one-hour realizations. The global analysis results provide useful information on their own — regarding the correlation between environmental condition and tower top acceleration, and correlation between tower top acceleration and other responses of interest — which are used as input in a decoupled analysis approach. The load effects and motions from the global analysis are applied on a detailed drivetrain model in a multi-body system (MBS) analysis tool. The local responses on bearings are then obtained from MBS analysis and post-processed for the correlation study. Although the maximum acceleration provides a good indication of the wave-induced loads, it is not seen to be a good predictor for significant fatigue damage on the main bearings in this case.

scholarly journals A Heuristic Approach for Inter-Facility Comparison of Results from Round Robin Testing of a Floating Wind Turbine in Irregular Waves

2021 ◽  
Vol 9 (9) ◽  
pp. 1030
Author(s):  
Sebastien Gueydon ◽  
Frances Judge ◽  
Eoin Lyden ◽  
Michael O’Shea ◽  
Florent Thiebaut ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Round Robin ◽  
Irregular Waves ◽  
Scale Model ◽  
Test Results ◽  
Floating Platform ◽  
Global Trends ◽  
Irregular Wave ◽  
Floating Wind Turbine ◽  
Decay Tests

This paper introduces metrics developed for analysing irregular wave test results from the round robin testing campaign carried out on a floating wind turbine as part of the EU H2020 MaRINET2 project. A 1/60th scale model of a 10 MW floating platform was tested in wave basins in four different locations around Europe. The tests carried out in each facility included decay tests, tests in regular and irregular waves with and without wind thrust, and tests to characterise the mooring system as well as the model itself. While response amplitude operations (RAOs) are a useful tool for assessing device performance in irregular waves, they are not easy to interpret when performing an inter-facility comparison where there are many variables. Metrics that use a single value per test condition rather than an RAO curve are a means of efficiently comparing tests from different basins in a more heuristic manner. In this research, the focus is on using metrics to assess how the platform responds with varying wave height and thrust across different facilities. It is found that the metrics implemented are very useful for extracting global trends across different basins and test conditions.

Numerical Analysis for Pipeline Installation by S-Lay Method

2010 ◽  
Author(s):  
Li-Zhong Wang ◽  
Feng Yuan ◽  
Zhen Guo
Keyword(s):  
Numerical Analysis ◽  
Numerical Model ◽  
Solution Process ◽  
Engineering Application ◽  
Influential Factors ◽  
Ocean Currents ◽  
Real Situation ◽  
Calm Water ◽  
Internal Forces ◽  
Seabed Stiffness

S-lay method is widely used in pipeline installation from shallow water to deep water for decades. However, previous researches on S-lay method are not so complete because they are based on some assumptions, such as calm water and rigid seabed, which make the results deviate from precision. In this paper, a novel numerical model for analyzing pipelines in the S-lay problem is proposed to investigate the overall configuration, internal forces and strain of the pipeline taking into account the influence of ocean currents and seabed stiffness. Such a model is of great advantage because it can properly consider many influential factors in the real situation, including the variation position of the liftoff point, the change of stinger radius, the influence of ocean currents, seabed stiffness and the strain of the pipeline. Moreover, the solution process of this model is easy and not time consuming, so it is suitable for engineering application.

Effect of Axial Acceleration on Drivetrain Responses in a Spar-Type Floating Wind Turbine

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Amir R. Nejad ◽  
Erin E. Bachynski ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Global Analysis ◽  
Correlation Study ◽  
Analysis Tool ◽  
Maximum Acceleration ◽  
Peak Period ◽  
Floating Wind Turbine ◽  
Axial Acceleration ◽  
Northern North Sea ◽  
Wave Induced

Common industrial practice for designing floating wind turbines is to set an operational limit for the tower-top axial acceleration, normally in the range of 0.2–0.3 g, which is typically understood to be related to the safety of turbine components. This paper investigates the rationality of the tower-top acceleration limit by evaluating the correlation between acceleration and drivetrain responses. A 5-MW reference drivetrain is selected and modeled on a spar-type floating wind turbine in 320 m water depth. A range of environmental conditions are selected based on the long-term distribution of wind speed, significant wave height, and peak period from hindcast data for the Northern North Sea. For each condition, global analysis using an aero-hydro-servo-elastic tool is carried out for six one-hour realizations. The global analysis results provide useful information on their own—regarding the correlation between environmental condition and tower top acceleration, and the correlation between tower top acceleration and other responses of interest—which are used as input in a decoupled analysis approach. The load effects and motions from the global analysis are applied on a detailed drivetrain model in a multibody system (MBS) analysis tool. The local responses on bearings are then obtained from MBS analysis and postprocessed for the correlation study. Although the maximum acceleration provides a good indication of the wave-induced loads, it is not seen to be a good predictor for significant fatigue damage on the main bearings in this case.

Non-Linear 3D Hydrodynamics of Floating Wind Turbine Compared Against Wave Tank Tests

2016 ◽  
Author(s):  
Nicolai F. Heilskov ◽  
Ole Svenstrup Petersen
Keyword(s):  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Cfd Simulation ◽  
Wave Structure ◽  
Point Of View ◽  
Body Motion ◽  
Irregular Waves ◽  
Floating Body ◽  
Wave Tank ◽  
Floating Wind Turbine

Assessment of wave-structure interaction in terms of combined hydrodynamic stability and structural survivability is paramount in extreme wave conditions. Components of CFD methodologies needed for accurately capturing the detailed motion of a floating wind turbine (FWT) in survival sea-state is the focus of the study. Physical wave tank tests of a Tension Leg Platform (TLP) concept with four moorings are applied as a first validation, due to its simplicity from a CFD point of view. Two different codes have been objects of study, namely the open source code OpenFOAM® with a flexible mesh approach and the commercial CFD code StarCCM+ with the overset mesh method. The influence of the surface capturing algorithm (VOF method) and the two-way coupling of the six degrees-of-freedom body motion solver and the hydrodynamic solver have been identified as the crucial components in CFD simulation of the FWT. A major advantage of StarCCM+ was that it does not suffer from the same sensitivity as OpenFOAM to the fact that motion of the floating body is strongly coupled to the solution of the hydrodynamics (a stiff FSI problem) which led to instability of the numerical solution. The results obtained with StarCCM+ are comparable with the measured motion of and tension forces on the TLP in both in regular waves and irregular waves.

Global Analysis of a Floating Wind Turbine Using an Aero-Hydro-Elastic Model: Part 1—Code Development and Case Study

2011 ◽  
Author(s):  
Harald Ormberg ◽  
Elizabeth Passano ◽  
Neil Luxcey
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Global Analysis ◽  
Offshore Wind Turbine ◽  
System Response ◽  
Elastic Model ◽  
Analysis Tool ◽  
Time Step ◽  
Floating Wind Turbine ◽  
Study Results

This paper describes the extension of a well proven state-of-the-art simulation tool for coupled floating structures to accommodate offshore wind turbine applications, both floating and fixed. All structural parts, i.e. rotor blades, hub, nacelle, tower, vessel and mooring system, are included in the finite element model of the complete system. The aerodynamic formulation is based on the blade element momentum theory. A control algorithm is used for regulation of blade pitch angle and electrical torque. The system response is calculated by nonlinear time domain analysis. This approach ensures dynamic equilibrium every time step and gives a proper time domain interaction between the blade dynamics, the mooring dynamics and the tower motions. The developed computer code provides a tool for efficient analysis of motions, support forces and power generation potential, as influenced by waves, wind, and current. Some key results from simulations with wind and wave loading are presented in the paper. The results are compared with results obtained with a rigid blade model and quasi-static model of the anchor lines. The modelled wind turbine is the NREL offshore 5-MW baseline wind turbine, specifications of which are publicly available. In the accompanying paper, Global Analysis of a Floating Wind Turbine Using an Aero-Hydro-Elastic Numerical Model. Part 2: Benchmark Study, results from the new analysis tool are benchmarked against results from other analysis tools.

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