Browsing by Author "Bredmose, Henrik"

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    Improved tank test procedures for scaled floating offshore wind turbines
    (2014) Müller, Kolja; Sandner, Frank; Bredmose, Henrik; Azcona, José; Manjock, Andreas; Pereira, Ricardo
    This study collects issues from previous tank test campaigns of scaled Floating Offshore Wind Turbines (FOWT), compares the different scaling methodologies, points out critical aspects and shows possible alternatives and recommendations for future tests depending on the specific objective. Furthermore, it gives practical recommendations for the modeling and construction of scaled rotors. The presented scaling procedure will be applied in tank tests within the EU Seventh Framework Program InnWind (ENERGY.2012.2.3.1 "Innovative wind conversion systems (10-20MW) for offshore applications").
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    Response of the International Energy Agency (IEA) Wind 15 MW WindCrete and Activefloat floating wind turbines to wind and second-order waves
    (2021) Mahfouz, Mohammad Youssef; Molins, Climent; Trubat, Pau; Hernández, Sergio; Vigara, Fernando; Pegalajar-Jurado, Antonio; Bredmose, Henrik; Salari, Mohammad
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    The TripleSpar campaign: validation of a reduced-order simulation model for floating wind turbines
    (2018) Lemmer, Frank; Yu, Wei; Cheng, Po Wen; Pegalajar-Jurado, Antonio; Borg, Michael; Mikkelsen, Robert F.; Bredmose, Henrik
    Different research groups have recently tested scaled floating offshore wind turbines including blade pitch control. A test conducted by the University of Stuttgart (Germany), DTU (Denmark) and CENER (Spain) at the Danish Hydraulic Institute (DHI) in 2016 successfully demonstrated a real-time blade pitch controller on the public 10MW TripleSpar semisubmersible concept at a scale of 1/60. In the presented work a reduced-order simulation model including control is compared against the model tests. The model has only five degrees of freedom and is formulated either in the time-domain or in the frequency-domain. In a first step the Morison drag coefficients are identified from decay tests as well as irregular wave cases. The identified drag coefficients depend clearly on the sea state, with the highest ones for the decay tests and small sea states. This is an important finding, for example for the design of a robust controller, which depends on the system damping. It is shown that the simplified model can well represent the dominant physical effects of the coupled system with a substantially reduced simulation time, compared to state-of-the-art models.