Influence of the Rotor Characterization on the Motion of a Floating Wind Turbine

2015 ◽  
Author(s):  
Sébastien Gueydon ◽  
Guillaume Venet ◽  
Gerson Fernandes
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Rotation Speed ◽  
Model Tests ◽  
Full Scale ◽  
Aerodynamic Damping ◽  
Common Solution ◽  
Floating Wind Turbine ◽  
Wave Basin ◽  
Low Reynolds

It is useful to complement model tests of a floating wind turbine with simulations mimicking the scaled-down turbine. Standard engineering tools have some short-comings to model a rotor at the very low Reynolds that Froude scaled wind and rotor’s rotation speed impose. The flow around an airfoil at the scale of a wave basin brings new distinct challenges than at full scale. The capacity of standard engineering tools for the design of wind turbines to capture this complexity may be questioned. Therefore, work-around solutions need to be proposed. This paper looks at a common solution that consists of optimizing the load coefficients of the rotor to reproduce the measured rotor loads. 3 variants of optimizations are applied to a semisubmersible floating wind turbine at scale 1/50th, the DeepCwind semisubmersible platform. The effects of the differences between these 3 methods on the motions of the floater in waves and wind are analyzed. In the absence of a controller for the rotor, no significant differences related to the induced aerodynamic damping was noticed, but an offset in the motion related to a thrust deficit was observed.

Methodology for Wind/Wave Basin Testing of Floating Offshore Wind Turbines

2012 ◽  
Author(s):  
Heather R. Martin ◽  
Richard W. Kimball ◽  
Anthony M. Viselli ◽  
Andrew J. Goupee
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Model Testing ◽  
Full Scale ◽  
Scale Model ◽  
Horizontal Axis Wind Turbine ◽  
Wind Turbine Aerodynamics ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines ◽  
Wave Basin

Scale model wave basin testing is often employed in the development and validation of large scale offshore vessels and structures by the oil and gas, military and marine industries. A basin model test requires less time, resources and risk than a full scale test while providing real and accurate data for model validation. As the development of floating wind turbine technology progresses in order to capture the vast deepwater wind energy resource, it is clear that model testing will be essential for the economical and efficient advancement of this technology. However, the scale model testing of floating wind turbines requires one to accurately simulate the wind and wave environments, structural flexibility and wind turbine aerodynamics, and thus requires a comprehensive scaling methodology. This paper presents a unified methodology for Froude scale testing of floating wind turbines under combined wind and wave loading. First, an overview of the scaling relationships employed for the environment, floater and wind turbine are presented. Afterward, a discussion is presented concerning suggested methods for manufacturing a high-quality, low turbulence Froude scale wind environment in a wave basin to facilitate simultaneous application of wind and waves to the model. Subsequently, the difficulties of scaling the highly Reynolds number-dependent wind turbine aerodynamics is presented in addition to methods for tailoring the turbine and wind characteristics to best emulate the full scale condition. Lastly, the scaling methodology is demonstrated using results from 1/50th scale floating wind turbine testing performed at MARIN’s (Maritime Research Institute Netherlands) Offshore Basin which tested the 126 m rotor diameter NREL (National Renewable Energy Lab) horizontal axis wind turbine atop three floating platforms: a tension-leg platform, a spar-buoy and a semi-submersible. The results demonstrate the methodology’s ability to adequately simulate full scale global response of floating wind turbine systems.

Additional Wind/Wave Basin Testing of the DeepCwind Semi-Submersible With a Performance-Matched Wind Turbine

2014 ◽  
Author(s):  
Andrew J. Goupee ◽  
Matthew J. Fowler ◽  
Richard W. Kimball ◽  
Joop Helder ◽  
Erik-Jan de Ridder
Keyword(s):  
Wind Speed ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Wave ◽  
Full Scale ◽  
Floating Wind Turbine ◽  
Wave Basin ◽  
Global Performance ◽  
Thrust Forces ◽  
A Performance

In 2011 the DeepCwind Consortium, led by the University of Maine (UMaine), performed an extensive series of floating wind turbine model tests at the Maritime Research Institute Netherlands (MARIN) offshore basin. These tests, which were conducted at 1/50th scale, investigated the response of three floating wind turbine concepts subjected to simultaneous wind and wave environments. The wind turbine blades utilized for the tests were geometrically-similar models of those found on the National Renewable Energy Laboratory (NREL) 5 MW reference wind turbine and performed poorly in the Froude-scaled, low-Reynolds number wind environment. As such, the primary aerodynamic load produced by the wind turbine, thrust, was drastically lower than expected for a given Froude-scaled wind speed. In order to obtain appropriate mean thrust forces for conducting the global performance testing of the floating wind turbines, the winds speeds were substantially raised beyond the target Froude-scale values. While this correction yielded the desired mean thrust load, the sensitivities of the thrust force due to changes in the turbine inflow wind speed, whether due to wind gusts or platform motion, were not necessarily representative of the full-scale system. In hopes of rectifying the wind turbine performance issue for Froude-scale wind/wave basin testing, efforts have been made by UMaine, Maine Maritime Academy and MARIN to design performance-matched wind turbines that produce the correct thrust forces when subjected to Froude-scale wind environments. In this paper, an improved, performance-matched wind turbine is mounted to the DeepCwind semi-submersible platform investigated in 2011 (also studied in the International Energy Association’s OC4 Phase II Project) and retested in MARIN’s offshore basin with two major objectives: 1) To demonstrate that the corrective wind speed adjustments made in the earlier DeepCwind tests produced realistic global performance behaviors and 2) To illustrate the increased capability for simulating full-scale floating wind turbine responses that a performance-matched turbine has over the earlier, geometrically-similar design tested. As an example of this last point, this paper presents select results for coupled wind/wave tests with active blade pitch control made possible with the use of a performance-matched wind turbine. The results of this paper show that the earlier DeepCwind tests produced meaningful data; however, this paper also illustrates the immense potential of using a performance-matched wind turbine in wind/wave basin model tests for floating wind turbines.

Methodology for Wind/Wave Basin Testing of Floating Offshore Wind Turbines

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Heather R. Martin ◽  
Richard W. Kimball ◽  
Anthony M. Viselli ◽  
Andrew J. Goupee
Keyword(s):  
Wind Turbine ◽  
Model Test ◽  
Wind Turbines ◽  
Model Testing ◽  
Full Scale ◽  
Scale Model ◽  
Horizontal Axis Wind Turbine ◽  
Wind Turbine Aerodynamics ◽  
Floating Wind Turbine ◽  
Wave Basin

Scale-model wave basin testing is often employed in the development and validation of large-scale offshore vessels and structures by the oil and gas, military, and marine industries. A basin-model test requires less time, resources, and risk than a full-scale test, while providing real and accurate data for numerical simulator validation. As the development of floating wind turbine technology progresses in order to capture the vast deep-water wind energy resource, it is clear that model testing will be essential for the economical and efficient advancement of this technology. However, the scale model testing of floating wind turbines requires accurate simulation of the wind and wave environments, structural flexibility, and wind turbine aerodynamics and thus requires a comprehensive scaling methodology. This paper presents a unified methodology for Froude scale model testing of floating wind turbines under combined wind and wave loading. First, an overview of the scaling relationships employed for the environment, floater, and wind turbine are presented. Afterward, a discussion is presented concerning suggested methods for manufacturing a high-quality, low-turbulence Froude scale wind environment in a wave basin to facilitate simultaneous application of wind and waves to the model. Subsequently, the difficulties of scaling the highly Reynolds number–dependent wind turbine aerodynamics is presented in addition to methods for tailoring the turbine and wind characteristics to best emulate the full-scale condition. Lastly, the scaling methodology is demonstrated using results from 1/50th-scale floating wind turbine testing performed at the Maritime Research Institute Netherlands (MARIN) Offshore Basin. The model test campaign investigated the response of the 126 -m rotor diameter National Renewable Energy Lab (NREL) horizontal axis wind turbine atop three floating platforms: a tension-leg platform, a spar-buoy, and a semisubmersible. The results highlight the methodology's strengths and weaknesses for simulating full-scale global response of floating wind turbine systems.

Design and Testing of Scale Model Wind Turbines for Use in Wind/Wave Basin Model Tests of Floating Offshore Wind Turbines

2013 ◽  
Author(s):  
Matthew J. Fowler ◽  
Richard W. Kimball ◽  
Dale A. Thomas ◽  
Andrew J. Goupee
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Model Tests ◽  
Full Scale ◽  
Offshore Wind ◽  
Scale Model ◽  
Offshore Wind Turbines ◽  
Floating Offshore Wind Turbines ◽  
Wave Basin ◽  
Scale Design

Model basin testing is a standard practice in the design process for offshore floating structures and has recently been applied to floating offshore wind turbines. 1/50th scale model tests performed by the DeepCwind Consortium at Maritime Research Institute Netherlands (MARIN) in 2011 on various platform types were able to capture the global dynamic behavior of commercial scale model floating wind turbine systems; however, due to the severe mismatch in Reynolds number between full scale and model scale, the strictly Froude-scaled, geometrically similar wind turbine underperformed greatly. This required significant modification of test wind speeds to match key wind turbine aerodynamic loads, such as thrust. To execute more representative floating wind turbine model tests, it is desirable to have a model wind turbine that more closely matches the performance of the full scale design. This work compares the wind tunnel performance, under Reynolds numbers corresponding to model test Froude-scale conditions, of an alternative wind turbine designed to emulate the performance of the National Renewable Energy Laboratory (NREL) 5 MW turbine. Along with the test data, the design methodology for creating this wind turbine is presented including the blade element momentum theory design of the performance-matched turbine using the open-source tools WT_Perf and XFoil. In addition, a strictly Froude-scale NREL 5 MW wind turbine design is also tested to provide a basis of comparison for the improved designs. While the improved, performance-matched turbine was designed to more closely match the NREL 5 MW design in performance under low model test Reynolds numbers, it did not maintain geometric similitude in the blade chord and thickness orientations. Other key Froude scaling parameters, such as blade lengths and rotor operational speed, were maintained for the improved designs. The results of this work support the development of protocols for properly designing scale model wind turbines that emulate the full scale design for Froude-scale wind/wave basin tests of floating offshore wind turbines.

Using Nonlinear Wave Kinematics to Estimate the Loads on Offshore Wind Turbines in 3-Hour Sea States

2018 ◽  
Author(s):  
Tim Bunnik ◽  
Erik-Jan de Ridder
Keyword(s):  
Wind Turbine ◽  
Nonlinear Wave ◽  
Wind Turbines ◽  
Wave Model ◽  
Breaking Waves ◽  
Model Tests ◽  
Offshore Wind ◽  
Wave Loads ◽  
Offshore Wind Turbines ◽  
Wave Basin

The effects of operational wave loads and wind loads on offshore mono pile wind turbines are well understood. For most sites, however, the water depth is such that breaking or near-breaking waves will occur causing impulsive excitation of the mono pile and consequently considerable stresses, displacements and accelerations in the monopile, tower and turbine. As has been shown in earlier, recent publications, Computational Fluid Dynamics (CFD) can be used to accurately analyze wave impacts on offshore wind turbines. However, it is not yet well suited to study the statistical variability of wave impact loads in long-duration sea states, and thus estimate the ULS and ALS loads for which a wind turbine has to be designed. An alternative, simplified approach, is the use of a Morison model in which the kinematics (water particle velocities and accelerations) from a nonlinear wave model are used. For long-crested waves the nonlinear wave model can be run in a 2D mode and is therefore relatively cheap. In this paper model tests for steep and breaking waves on an offshore wind turbine are compared with results from the Morison model. First, a deterministic comparison is made between the wave loads from the model tests and the simulation model (simulating the same 3-hour wave realization as in the basin), which turns out to be difficult because of differences between wave reflections in the wave basin (a physical beach) and the numerical wave model (absorbing boundary condition). Second, a statistical comparison is made by comparing with different wave realizations measured in the wave basin.

Development of a Scaled-Down Floating Wind Turbine for Offshore Basin Testing

2014 ◽  
Author(s):  
Erik-Jan de Ridder ◽  
William Otto ◽  
Gert-Jan Zondervan ◽  
Fons Huijs ◽  
Guilherme Vaz
Keyword(s):  
Wind Turbine ◽  
Wind Velocity ◽  
Scaling Laws ◽  
Scale Effects ◽  
Model Testing ◽  
Model Tests ◽  
Full Scale ◽  
Pitch Control ◽  
Model Scale ◽  
Floating Wind Turbine

In the last years MARIN has been involved in an increasing number of projects for the offshore wind industry. New techniques in model testing and numerical simulations have been developed in this field. In this paper the development of a scaled-down wind turbine operating on a floating offshore platform, similar to the well-known 5MW NREL wind turbine is discussed. To simulate the response of a floating wind turbine correctly it is important that the environmental loads due to wind, waves and current are in line with full scale. For dynamic similarity on model scale, Froude scaling laws are used successfully in the Offshore industry for the underwater loads. To be consistent with the underwater loads, the winds loads have to be scaled according to Froude as well. Previous model tests described by Robertson et al [1] showed that a geometrically-scaled turbine generated a lower thrust and power coefficient with a Froude-scaled wind velocity due to the strong Reynolds scale effects on the flow. To improve future model testing, a new scaling method for the wind turbine blades was developed originally by University of Maine, and here improved and applied. In this methodology, the objective is to obtain power and thrust coefficients which are similar to the full-scale turbine in Froude-scaled wind. This is obtained by changing the geometry of the blades in order to provide thrust equality between model and full scale, and can therefore be considered as a “performance scaling”. This method was then used to design and construct a new MARIN Stock Wind Turbine (MSWT) based on the NREL 5MW wind turbine blade, including an active blade pitch control to simulate different blade pitch control systems. MARIN’s high-quality wind setup in combination with the new model scale stock wind turbine was used for testing the GustoMSC Tri-Floater semi-submersible as presented in Figure 1, including an ECN active blade pitch control algorithm. From the model tests it was concluded that the measured thrust versus wind velocity characteristics of the new MSWT were in line with the full scale prediction and with CFD (Computational Fluid Dynamics) results.

Model Tests for a Floating Wind Turbine on Three Different Floaters

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Bonjun J. Koo ◽  
Andrew J. Goupee ◽  
Richard W. Kimball ◽  
Kostas F. Lambrakos
Keyword(s):  
Wind Turbine ◽  
Wind Turbines ◽  
Wind Farms ◽  
Model Tests ◽  
Experimental Comparison ◽  
Floating Platform ◽  
Scaled Model ◽  
Advantages And Disadvantages ◽  
Floating Wind Turbine ◽  
Floating Platforms

Wind energy is a promising alternate energy resource. However, the on-land wind farms are limited by space, noise, and visual pollution and, therefore, many countries build wind farms near the shore. Until now, most offshore wind farms have been built in relatively shallow water (less than 30 m) with fixed tower type wind turbines. Recently, several countries have planned to move wind farms to deep water offshore locations to find stronger and steadier wind fields as compared to near shore locations. For the wind farms in deeper water, floating platforms have been proposed to support the wind turbine. The model tests described in this paper were performed at MARIN (maritime research institute netherlands) with a model setup corresponding to a 1:50 Froude scaling. The wind turbine was a scaled model of the national renewable energy lab (NREL) 5 MW horizontal axis reference wind turbine supported by three different generic floating platforms: a spar, a semisubmersible, and a tension-leg platform (TLP). The wave environment used in the tests is representative of the offshore in the state of Maine. In order to capture coupling between the floating platform and the wind turbine, the 1st bending mode of the turbine tower was also modeled. The main purpose of the model tests was to generate data on coupled motions and loads between the three floating platforms and the same wind turbine for the operational, design, and survival seas states. The data are to be used for the calibration and improvement of the existing design analysis and performance numerical codes. An additional objective of the model tests was to establish the advantages and disadvantages among the three floating platform concepts on the basis of the test data. The paper gives details of the scaled model wind turbine and floating platforms, the setup configurations, and the instrumentation to measure motions, accelerations, and loads along with the wind turbine rpm, torque, and thrust for the three floating wind turbines. The data and data analysis results are discussed in the work of Goupee et al. (2012, “Experimental Comparison of Three Floating Wind Turbine Concepts,” OMAE 2012-83645).

Blade loading performance of a floating wind turbine in wave basin model tests

2020 ◽  
Vol 199 ◽  
pp. 107061 ◽  
Author(s):  
Binrong Wen ◽  
Zhanwei Li ◽  
Zhihao Jiang ◽  
Xinliang Tian ◽  
Xingjian Dong ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Model Tests ◽  
Blade Loading ◽  
Floating Wind Turbine ◽  
Wave Basin

scholarly journals UNAFLOW: a holistic experiment about the aerodynamics of floating wind turbines under imposed surge motion

2021 ◽  
Author(s):  
Alessandro Fontanella ◽  
Ilmas Bayati ◽  
Robert Mikkelsen ◽  
Marco Belloli ◽  
Alberto Zasso
Keyword(s):  
Wind Tunnel ◽  
Wind Turbine ◽  
Wind Turbines ◽  
Unsteady Aerodynamics ◽  
Model Tests ◽  
Tip Vortex ◽  
Scale Model ◽  
Floating Wind Turbine ◽  
Floating Offshore Wind Turbines ◽  
Sectional Model

Abstract. Floating offshore wind turbines are subjected to large motions because of the additional degrees of freedom offered by the floating foundation. The rotor operates in highly dynamic inflow conditions and this is deemed to have a significant effect on the aerodynamic loads, as well as on the wind turbine wake. Floating wind turbines and floating farms are designed by means of numerical tools, that have to model these unsteady aerodynamic phenomena to be predictive of reality. Experiments are needed to get a deeper understanding of the unsteady aerodynamics, and hence leverage this knowledge to develop better models, as well as to produce data for the validation and calibration of the existing tools. This paper presents a wind-tunnel scale-model experiment about the unsteady aerodynamics of floating wind turbines that followed a radically different approach than the other existing experiments. The experiment covered any aspect of the problem in a coherent and structured manner, that allowed to produce a low-uncertainty data for the validation of numerical model. The data covers the unsteady aerodynamics of the floating wind turbine in terms of blade forces, rotor forces and wake. 2D sectional model tests were carried to study the aerodynamics of a low-Reynolds blade profile subjected to a harmonic variation of the angle of attack. The lift coefficient shows an hysteresis cycle that extends in the linear region and grows in strength for higher motion frequencies. The knowledge gained in 2D sectional model tests was exploited to design the rotor of a 1/75 scale model of the DTU 10MW that was used to perform imposed surge motion tests in a wind tunnel. The tower-top forces were measured for several combinations of mean wind speed, surge amplitude and frequency to assess the effect of unsteady aerodynamics on the response of the system. The thrust force, that plays a crucial role in the along-wind dynamics of a floating wind turbine mostly follows the quasi-steady theory. The near-wake of the wind turbine was studied by means of hot-wire measurements, and PIV was utilized to visualize the tip vortex. It is seen that the wake energy is increased in correspondence of the motion frequency and this is likely to be associated with the blade-tip vortex, which travel speed is modified in presence of surge motion.

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