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Validation of Offshore load simulations using measurement data from the DOWNVInD project. M. Seidel, F. Ostermann – REpower Systems AG Curvers, A.P.W.M. – Energy research Centre of the Netherlands (ECN), Petten, The Netherlands
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Validation of Offshore load simulations using measurement data from the DOWNVInD project M. Seidel, F. Ostermann – REpower Systems AG Curvers, A.P.W.M. – Energy research Centre of the Netherlands (ECN), Petten, The Netherlands Kühn, M.; Kaufer, D. – Endowed Chair of Wind Energy, University of Stuttgart, Germany Böker, C. – ForWind, Institute for Steel Construction, Leibniz University Hannover, Germany Stand 06/09
Agenda Introduction DOWNVInD measurements Coupling methods Comparison of measurements with simulation Summary and outlook
Blade modes (flap & edge) Global support structure mode Local bracing mode Introduction What is integrated analysis and why is it important? • (Turbulent) wind field • (Stochastic) wave loading on substructure • Complete turbine model (incl. e.g. electrical system and controller) • Blade aerodynamics • Structural dynamics
DOWNVInD measurements DOWNVInD (Beatrice Demonstrator): The DOWNVInD Project has received funding from the Scottish Executive, the UK Department of Trade and Industry, and the European Commission. The support of these organizations is gratefully acknowledged.
DOWNVInD measurements Aim of the measurement programme: • Gain knowledge of the real load spectrum to assess fatigue lifetime of the main components: substructure, tower and rotor blades; • To validate the load prediction models to increase the reliability of the future 1.000 MW wind farm. • Measurement programme has been drafted in close cooperation between ECN (NL) and Teknikgruppen (SE); both involved in the evaluation programme
DOWNVInD measurements Instrumentation plan: • Rotor blades • bending moments • Nacelle • wind speed • Nacelle • main shaft bending and torsion • accelerations (5) • rotor position • rotor rotational speed • pitch angle • turbine status • Tower top • bending moments • shear forces • Tower base • bending moments • accelerations (3) • electric power Dante systems In nacelle and tower base Total: 60 signals 1,2 Gb per day • Substructure/Jacket • bending moments • axial forces • Wind speed with Lidar on Beatrice A • Wave measurements with buoy
Coupling methods Sequential coupling: • Substructure is reduced to 6x6 DOFs by Guyan reduction (static reduction) • System matrices (mass, stiffness, damping) and (wave) load time histories are generated inASAS(NL) and used in Flex 5 • Retrieval run generates member forces in complete substructure Seidel, M. et. al.: Integrated analysis of wind and wave loading for complex support structures of Offshore Wind Turbines. Conference Proceedings Offshore Wind 2005, Copenhagen 2005.
Coupling methods Full coupling: • Flex 5 and ASAS(NL) or Poseidon are running simultaneously • Information is exchanged in each time step • NO reduction of substructure is employed – system matrices are fully retained Kaufer, D. et. al.: Integrated Analysis of the Dynamics of Offshore Wind Turbines with Arbitrary Support Structures. Proc. of EWEC 2009. Marseille: EWEC, 2009.
Coupling methods Validation of full coupling: • Several benchmark tests against Flex 5 stand-alone • Increasing complexity (dead-weight, static wind, turbulent wind) • Onshore foundation and monopile • Validation with both ASAS(NL) and Poseidon • Very good agreement of results
Comparison of sequential to full coupling Comparison at tower bottom (global response):
Comparison of sequential to full coupling Comparison at a jacket brace (local response): Full coupling: Red Sequential coupling: Black
Comparison of measurements with simulation Comparison for local member force in a jacket leg: Measurement: Red Simulation (full coupling): Black
Comparison of measurements with simulation Comparison for an in-plane moment in a jacket brace: Measurement: Red Simulation (full coupling): Black
Summary and outlook Summary: • Coupling methods work well for design calculations • Sequential coupling conservative compared to full coupling • Comparison with measurements indicates good performance Outlook: • Further validation required with more complete measurements • Measurements to be used: RAVE (alpha ventus), about to be installed now