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J. Mar. Sci. Eng. 2018, 6(4), 118; https://doi.org/10.3390/jmse6040118

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

Stuttgart Wind Energy (SWE), University of Stuttgart, 70569 Stuttgart, Germany
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Received: 30 August 2018 / Revised: 26 September 2018 / Accepted: 5 October 2018 / Published: 12 October 2018
(This article belongs to the Special Issue Offshore Wind Structures)
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Abstract

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. View Full-Text
Keywords: floating wind turbine; viscous drag identification; parametric viscous drag; Morison’s equation; frequency-domain; wind turbine control; low-order modeling floating wind turbine; viscous drag identification; parametric viscous drag; Morison’s equation; frequency-domain; wind turbine control; low-order modeling
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Lemmer, F.; Yu, W.; Cheng, P.W. Iterative Frequency-Domain Response of Floating Offshore Wind Turbines with Parametric Drag. J. Mar. Sci. Eng. 2018, 6, 118.

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