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Introduction of ice loads in overall simulation of offshore wind turbines

: Heinonen, J.; Hetmanczyk, S.; Strobel, M.

Canadian Hydraulics Centre -CHC-, Ottawa:
21st International Conference on Port and Ocean Engineering under Arctic Conditions 2011, POAC 2011. Proceedings. CD-ROM : July 10 - 14, 2011, Montréal, Canada
Montreal: NRC Canada, 2011
International Conference on Port and Ocean Engineering under Arctic Conditions (POAC) <21, 2011, Montreal>
Conference Paper
Fraunhofer IWES ()

Due to the global aim of reducing the CO2 emissions, renewable energy production comes more and more into focus. Offshore wind energy is one of the most promising technologies especially in northern regions because of the high and constant wind velocities. The challenges among the others are ice loads and especially ice induced vibrations, which are one of the most significant uncertainties in offshore wind turbine design. Recent investigations in the field of ice mechanics lead to the conclusion that the ice failure has a strong dependency on the dynamic ice-structure interaction. Therefore, a self excited ice structure interaction model by Määttänen-Blenkarn was implemented in a aero-hydro-servo-elastic simulation tool utilizing the state-of-the-art modelling language Modelica. The simulation platform OnWind with a simplified wind turbine model was utilized for simulations. The structural model of an offshore wind turbine consisted of a single wind turbine support str ucture (tower and vertical monopile substructure) with a representing dead mass on tower top. The implemented ice models were validated by comparing results with existing simulation tools. The influence of ice velocity on the displacement response in ice-structure interaction was studied by two configurations representing different structural stiffness due to various water depths: 30m ("soft") and 10m ("stiff"). Both configurations were sensitive on frequency lock-in vibration superposed by 1st natural frequency and other frequencies depending on the ice velocity. Vibration of stiffer structure indicated that multiple eigenmodes contributed to lock-in vibration. It was observed that Määttänen-Blenkarn model was not able to simulate either continuous brittle crushing or intermittent ice crushing. Further investigation should be concentrated to improve the ice load model to describe various ice failure phenomena. Simulations with OnWind software were carried out successfully creating a promising basis