Abstract
Abstract. A model for quick load analysis, QuLA, of an offshore wind turbine substructure is presented. The aerodynamic rotor loads and damping are pre-computed for a land-based configuration. The dynamic structural response is represented by the first global fore-aft mode only and is computed in the frequency domain with phases using the equation of motion. The model is compared to the state-of-the-art aeroelastic code Flex5. Both lifetime fatigue and extreme loads are considered in the comparison. In general there is good agreement between the two models. Some deviations for the sectional forces are explained in terms of the model simplifications. The differences in the sectional moments are found to be within 10 % for the fatigue load case and 10 % for the extreme load condition.
Highlights
In order to ensure cost-efficient offshore wind farms, it is necessary to optimize the design
Since the aerodynamic forces are included as point forces in QuLA and since the equation of motion is solved in frequency domain, the aerodynamic damping can only be added as a viscous linear damping force, where the damping coefficient is a function of the mean wind speed
The model solves the equation of motion in the frequency domain and uses precalculated aerodynamic forces and damping as a function of the wind speed
Summary
In order to ensure cost-efficient offshore wind farms, it is necessary to optimize the design. Schafhirt et al (2015) combined a substructuring technique, which is based on the principle of superposition of impulse responses, with the power of modern generalpurpose graphics processing units to compute the response of an offshore wind turbine subject to rotor loads This method to perform simplified analysis of offshore wind turbines was found to have the same accuracy as standard aeroelastic models for distinct output locations as the overturning moment in the bottom of the tower but is 40 times faster for the case in which only rotor loading on the substructure is considered. In the present paper a model for quick load analysis, QuLA, is presented This is a fast model for the calculation of dynamic loads of an offshore wind turbine tower and foundation. In the present paper the results are, compared to the previously published paper, improved mainly due to changes in the calculations of the aerodynamic damping and the addition of load case 1.3 to extend the analysis
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