The TripleSpar Campaign: Validation of a Reduced-Order Simulation Model for Floating Wind Turbines

Lemmer, Frank; Yu, Wei; Cheng, Po Wen; Pegalajar‐Jurado, Antonio; Borg, Michael; Mikkelsen, Robert Flemming; Bredmose, Henrik

doi:10.1115/omae2018-78119

Cited by 5 publications

(9 citation statements)

References 17 publications

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“…Yet, some of them agree on the importance of viscous effects to correctly predict slow-drift response. Lemmer et al [14] compared a loworder model that included slow-drift loads through the Newman approximation and Morison drag based on the relative floater velocity to test data. The drag coefficients were tuned for different sea states to match the measured response,…”

Section: Introductionmentioning

confidence: 99%

Reproduction of slow-drift motions of a floating wind turbine using second-order hydrodynamics and Operational Modal Analysis

Pegalajar‐Jurado

Bredmose

2019

Marine Structures

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Slow-drift forcing and damping are important for an accurate reproduction of the low-frequency motion of floating offshore wind turbines. In this study we present a numerical model that includes both inviscid slow-drift forcing through full quadratic transfer functions (QTFs) and viscous forcing. To accommodate a linear damping matrix that represents all the damping effects on the floater, the classical Morison formulation of the drag forcing with relative velocity is simplified into a pure forcing term and a linear constant damping term. The frequency-dependent radiation properties are also replaced by constant matrices. We investigate the application of Operational Modal Analysis (OMA) to estimate the damping ratios from the test data, and also pursue a calibration method where the linear damping is calibrated in the modal space and subsequently transformed back to the physical space. The model is compared to wave basin data for four environmental conditions including the 50-year sea state. The damping ratios estimated with OMA generally increase with the sea state. The measured response can be generally well reproduced by the model when the damping is calibrated for each sea state. Due to the neglection of firstorder motion effects in the applied QTFs and to the damping introduced by the mooring lines, however, the surge response is underpredicted for the severe sea states, and the yaw motion is always underpredicted. The commonly used approach where the damping is calibrated to the decay tests is found to provide less accurate results than the approach of calibrating the modal damping ratios

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Section: Introductionmentioning

confidence: 99%

Reproduction of slow-drift motions of a floating wind turbine using second-order hydrodynamics and Operational Modal Analysis

Pegalajar‐Jurado

Bredmose

2019

Marine Structures

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“…The present study addresses the question of the load-case dependence of the drag coefficients for FOWTs. As we showed experimentally in [28], the viscous damping properties of FOWTs can vary significantly, depending on the load case. This is due to the strong Reynolds dependence (Re =vD/ν, with velocity amplitudev, characteristic length D and kinematic viscosity ν) and also a dependence on the Keulegan-Carpenter number (KC) (KC =vT/D, with period of oscillation T) of the drag coefficients, see ([29], Chapter 7) and, additionally, the body surface roughness [30].…”

Section: Hydrodynamic Viscous Dragmentioning

confidence: 65%

“…Thus, the heave plate drag is a function of the dynamic response of the FOWT. The drag values of [32] could be confirmed for FOWT model tests in [28] for the public TripleSpar design [33], which will be used in this work.…”

Section: Hydrodynamic Viscous Dragmentioning

confidence: 91%

“…The experimental model was tested in a scale of 1:60 in 2016 at the Danish Hydraulic Institute (DHI) with results presented in [5,28,39]. The test program included irregular wave with wind Load Cases (LCs) with different significant wave heights H s and peak spectral periods T p .…”

Section: Reference Designmentioning

confidence: 99%

“…The parameterization of the column drag coefficients C D,ik is difficult due to their dependence on both Reynolds and KC-number, as described in the Introduction. In [28], the heave plate drag C D,hp was identified for coupled model tests of the TripleSpar, including the wind turbine and controller. The identified drag compares well with the values published by Tao et al ([32], p. 1012).…”

Section: Parametric Dragmentioning

confidence: 99%

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Iterative Frequency-Domain Response of Floating Offshore Wind Turbines with Parametric Drag

Lemmer¹,

Yu²,

Cheng³

2018

JMSE

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Methods for coupled aero-hydro-servo-elastic time-domain simulations of Floating Offshore Wind Turbines (FOWTs) have been successfully developed. One of the present challenges is a realistic approximation of the viscous drag of the wetted members of the floating platform. This paper presents a method for an iterative response calculation with a reduced-order frequency-domain model. It has heave plate drag coefficients, which are parameterized functions of literature data. The reduced-order model does not represent more than the most relevant effects on the FOWT system dynamics. It includes first-order and second-order wave forces, coupled with the wind turbine structural dynamics, aerodynamics and control system dynamics. So far, the viscous drag coefficients are usually defined as constants, independent of the load cases. With the computationally efficient frequency-domain model, it is possible to iterate the drag, such that it fits to the obtained amplitudes of oscillation of the different members. The results show that the drag coefficients vary significantly across operational load conditions. The viscous drag coefficients converge quickly and the method is applicable for concept-level design studies of FOWTs with load case-dependent drag.

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The Influence of Floating Turbine Dynamics on the Helix Wake Mixing Method

Van Den Berg,

De Tavernier,

Gutknecht

et al. 2024

J. Phys.: Conf. Ser.

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Wake mixing techniques like the Helix have shown to be effective at reducing the wake interaction between turbines, which improves wind farm power production. When these techniques are applied to a floating turbine it will excite movement. The type and magnitude of movement are dependent on floater dynamics. This work investigates four different floating turbines. Of these four turbines, two are optimised variants of the TripleSpar and Softwind platforms with enhanced yaw motion. The other two are the unaltered versions of these platforms. When the Helix is applied to all four floating turbines, the increased yaw motion of the optimised TripleSpar results in a reduction in windspeed whereas the optimised Softwind sees an increase in windspeed with increased yaw motion. From simulations using prescribed yaw motion at different phase offsets between blade pitch and yaw motion, we can conclude that this is the driving factor for this difference.

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The TripleSpar Campaign: Validation of a Reduced-Order Simulation Model for Floating Wind Turbines

Cited by 5 publications

References 17 publications

Reproduction of slow-drift motions of a floating wind turbine using second-order hydrodynamics and Operational Modal Analysis

Reproduction of slow-drift motions of a floating wind turbine using second-order hydrodynamics and Operational Modal Analysis

Iterative Frequency-Domain Response of Floating Offshore Wind Turbines with Parametric Drag

The Influence of Floating Turbine Dynamics on the Helix Wake Mixing Method

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