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

Martin, Heather R.; Kimball, Richard; Viselli, Anthony M.; Goupee, Andrew J.

doi:10.1115/1.4025030

Cited by 109 publications

(99 citation statements)

References 10 publications

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“…Other works have suggested placing a vortex generator in the model blade or increasing the roughness of the blade leading edge [17] to increase the rotor thrust owing to the greater turbulence around the model blade. However, it is most preferred to design a low-Reynolds-number model blade specific for the basin-model test as this can thoroughly mitigate the Reynolds number scaling effect (such as [19] [6,18]; and [14]. In this study, a model wind turbine rotor was optimally designed to have a rotor thrust matching that of the reference blade (after Froude scaling).…”

Section: Introductionmentioning

confidence: 99%

Design, analysis and test of a model turbine blade for a wave basin test of floating wind turbines

Han

et al. 2016

Renewable Energy

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a b s t r a c tFroude scaling is a generally reliable way to design models of floating wind turbines for wave basin testing. However, the resulting rotor thrust of the model is far lower than the Froude-scaled value of a full-size turbine, because the reduction in Reynolds number decreases the lift coefficients and increases the drag coefficients (the Reynolds number scaling effect). A 1/50th scale model wind turbine based on a NREL-5MW reference turbine is examined here. To mitigate the Reynolds number scaling effect in the model, the original aerofoils of the reference turbine (DU series and NACA 64-618) were replaced by an aerofoil at a low Reynolds number (NACA 4412). Such a model with aerofoil-adjusted blades was used in the mathematical optimization of rotor thrust. The design objective was to guarantee that while the rotor thrust of the model equalled the Froude-scaled rotor thrust of the reference, the smallest chord lengths were achieved, considering the weight control in building the model blade. The distribution of chord lengths fitted a fourth-order polynomial curve, and the distribution of twist angles along the blade fitted a second-order polynomial curve. The eight coefficients of the two curves were chosen as optimization variables, and pattern search method was used to solve the optimization model. The model blade was designed at zero pitch angle and further tested in FAST, a fully coupled simulation tool. A model test was conducted using the optimized blade geometry in the State Key Laboratory of Ocean Engineering in Shanghai, China, and the thrusts were compared with the predicted values.

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Section: Introductionmentioning

confidence: 99%

Design, analysis and test of a model turbine blade for a wave basin test of floating wind turbines

Han

et al. 2016

Renewable Energy

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“…Two sets of wind turbine characteristics were simulated. The first set is matched to the experimental performance of the Froude‐scaled model wind turbine and was developed previously at the University of Maine . This allows direct comparison of the purely physical results and the hybrid model results.…”

Section: Hardware Implementation and Test Setupmentioning

confidence: 98%

“…To match the true‐to scale thrust at rated wind speed, the blade pitch angles are set to 6.4° rather than 0°, and elevated wind speeds are used. The properties of the tested turbine are given in Table and further details are available in Martin et al The instrumentation is unchanged from previous tests, including rotor speed and torque measurements, a 3‐axis accelerometer, and a 6‐axis load cell at the tower top.…”

Section: Hardware Implementation and Test Setupmentioning

confidence: 99%

“…The most direct approach is to compensate for performance reductions through changes to the rotor geometry. Martin et al explored enlarging the blades, using special airfoils, and adding leading edge roughness to counter the lowered Reynolds number . Research at the University of Maine and the Maritime Research Institute of the Netherlands (MARIN) showed that using low‐Reynolds number airfoils with enlarged chord lengths can come close to matching true‐to‐scale thrust coefficients across typical operating conditions .…”

Section: Introductionmentioning

confidence: 99%

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Validation of a hybrid modeling approach to floating wind turbine basin testing

Hall

Goupee

2018

Wind Energy

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Hybrid modeling combining physical tests and numerical simulations in real time opens new opportunities in floating wind turbine research. Wave basin testing is an important validation step for floating support structure design, but current methods are limited by scaling problems in the aerodynamic loadings. Applying wind turbine loads with an actuation system controlled by a simulation that responds to the basin test offers a way to avoid scaling problems and reduce cost barriers for floating wind turbine design validation in realistic coupled conditions. In this work, a cable-based hybrid coupling approach is developed and implemented for 1:50-scale wave basin tests with the DeepCwind semisubmersible floating wind turbine. Tests are run with thrust loads provided by a numerical wind turbine model. Matching tests are run with physical wind loads using an above-basin wind maker. When the numerical submodel is set to match the aerodynamic performance of the physical scaled wind turbine, the results show good agreement with purely physical wind-wave tests, validating the hybrid model approach. Further hybrid model tests with simulated true-to-scale dynamic thrust loads and wind turbulence show noticeable differences and demonstrate the value of a hybrid model approach for improving the true-to-scale realism of floating wind turbine basin tests. KEYWORDS basin test, floating, hybrid model, hybrid testing, wind turbine 1 INTRODUCTION Scale-model testing of floating wind turbines, often considered an essential validation step in the design process, faces a difficult scaling problem. Two different fluid-structure-interaction domains need to be scaled simultaneously: the hydrodynamics of the floating support structure and the aerodynamics of the wind turbine. The dominance of different nondimensional ratios in each makes scaling without compensation cause discrepancies in the results. For example, a scaled-down floating wind turbine may require higher wind speeds and blade pitch adjustments to achieve the correct thrust force. 1 On top of this, there is the challenge of recreating a wind turbine's mechanical properties at small scale. For less advanced facilities, even providing controlled wind conditions above the wave basin may not be feasible. All these factors contribute to the scaling difficulty in floating wind turbine experiments. A number of approaches have arisen in recent years to counter some of these challenges, especially to do with the turbine aerodynamics. Müller et al review many of the challenges and options for floating wind turbine basin testing. 2 The most direct approach is to compensate for performance reductions through changes to the rotor geometry. Martin et al explored enlarging the blades, using special airfoils, and adding leading edge roughness to counter the lowered Reynolds number. 3 Research at the University of Maine and the Maritime Research Institute of the Netherlands(MARIN) showed that using low-Reynolds number airfoils with enlarged chord lengths can come close to matching true-to-s...

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“…Note that the thrust coefficient of the scale model at this operating point is considerably lower than that of the full-scale model; this is typical for a scale model with a large scale factor. 23,24 As mentioned in Section 2, the wind speed of 3.0 m/s was chosen to achieve the appropriate thrust force, and this is not a Froude-scaled wind speed. The matrices A, B 1 , B 2 , and C are unknowns to be determined so that the resulting system model (1) adequately represents the actual dynamical behavior of the FOWT scale model.…”

Section: Mathematical Model Construction By System Identificationmentioning

confidence: 99%

Experimental validation of model‐based blade pitch controller design for floating wind turbines: system identification approach

et al. 2017

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This paper discusses the model‐based design of a blade pitch controller for a floating offshore wind turbine (FOWT) scale model. A mathematical model of the FOWT is constructed from an input–output measurement in an experiment using system identification. The blade pitch controller is designed by an H∞ control method, and the effectiveness of the controller is evaluated by means of a basin experiment using the FOWT scale model. The results show that the blade pitch controller is effective in reducing platform pitch motion and rotor speed fluctuation. Copyright © 2017 John Wiley & Sons, Ltd.

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

Cited by 109 publications

References 10 publications

Design, analysis and test of a model turbine blade for a wave basin test of floating wind turbines

Design, analysis and test of a model turbine blade for a wave basin test of floating wind turbines

Validation of a hybrid modeling approach to floating wind turbine basin testing

Experimental validation of model‐based blade pitch controller design for floating wind turbines: system identification approach

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