Hansen, Anders Melchior

Larsen, Torben J.

Yde, Anders

The present work investigates the influence of using different ways of interfacing wind turbine model and foundation on loads in the combined structure. In the design procedure for offshore wind turbines it is common that foundation and wind turbine design loads are obtained in two sequential steps where firstly; the wind turbine designer defines the interface forces and moments in the interface point to the foundation based on either fixed or flexible boundary condition at the interface, and secondly; the foundation designer then uses those loads combined with additional wave and current forces to obtain the design loads for the foundation. The dynamic interaction between the wind turbine and foundation is left out in that procedure. Herein, three different design methodologies are applied to the same offshore wind turbine with identical turbulent wind (18 m/s) and irregular waves (Hs=6 m/Tp=10 s). The 5MW NREL reference turbine [1] on a jacket foundation from IEA Wind Task 30 OC4 [2] is used, and the differences in the design loads are compared using the aeroelastic code, HAWC2 [3]

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 20, 2017Influence of foundation model complexity on the design loads for offshore WTG onjacket foundationHansen, Anders Melchior; Larsen, Torben J.; Yde, AndersPublication date:2013Link back to DTU OrbitCitation (APA):Hansen, A. M., Larsen, T. J., & Yde, A. (2013). Influence of foundation model complexity on the design loads foroffshore WTG on jacket foundation. Poster session presented at European Wind Energy Conference &Exhibition 2013, Vienna, Austria.References Conclusion Modelling approaches INFLUENCE OF FOUNDATION MODEL COMPLEXITY ON THE DESIGN  LOADS FOR OFFSHORE WTG ON JACKET FOUNDATION Anders M. Hansen, Torben J. Larsen, Anders Yde Department of Wind Energy, Technical University of Denmark  PO.ID 123  1) Fully Coupled model         In the fully coupled model, both jacket foundation and wind turbine are combined into one HAWC2 model. This is considered to be the most accurate solution but it  also  has the highest computational cost. (reference case)                                                                                                                                        2) Sequential coupled model        In the sequential coupled model, the load calculations are split into two separate steps. First the turbine loads are obtained from a simulation with a full flexible turbine on an equivalent monopile that represents the stiffness of the jacket. Then the loads are transferred at the coupling point (interface point between jacket/monopile and tower base) to the jacket which is simulated with wave loadings.      3 ) Super Element/model reduction model        In the super element model, the HAWC2 jacket model is condensed into a newly developed super element and then combined with the wind turbine model at an interface point.  The super element is based on a reduction of states of the full foundation model, leaving only a small number of new states (6 in this case) compared to the number of original states (1200), and thus saves computer time during the design load simulations.  The present work investigates the influence of using different ways of interfacing wind turbine model and foundation on loads in the combined structure. In the design procedure for offshore wind turbines it is common that foundation and wind turbine design loads are obtained in two sequential steps where firstly; the wind turbine designer defines the interface forces and moments in the interface point to the foundation based on either fixed or flexible boundary condition at the interface, and secondly; the foundation designer then uses those loads combined with additional wave and current forces to obtain the design loads for the foundation. The dynamic interaction between the wind turbine and foundation is left out in that procedure.  Herein, three different design methodologies are applied to the same offshore wind turbine with identical turbulent wind (18 m/s) and irregular waves (Hs=6 m/Tp=10 s). The 5MW NREL reference turbine [1] on a jacket foundation from IEA Wind Task 30 OC4 [2] is used, and the differences in the design loads are compared using the aeroelastic code, HAWC2 [3].  The super element methodology has been implemented in HAWC2 during this study and the preliminary results indicate that the super element approach is very promising. However, further investigation into which and how many reduced DOFs are necessary in the super element is needed. A comparison between reaction forces simulated by the 3 methodologies shows that the correlation between the 3 methodologies is good, however, both the super element and the sequential approaches overestimate structural loads. The reason for this needs further investigation. Abstract  Results       EWEA 2013, Vienna, Austria: Europe’s Premier Wind Energy Event  1. J. Jonkman, S. Butterfield, W. Musial, and G. Scott. Definition of a 5-MW reference wind turbine for offshore system development. Technical Report NREL/TP-500- 38060, NREL, 2009. 2. Vorpahl, F., Popko, W., and Kaufer, D., 2011, “Description of a basic model of the "UpWind reference jacket" for code comparison in the OC4 project under IEA Wind Annex 30.” Tech. rep., Frauenhofer university.  3. T. J. Larsen and A. M. Hansen. How to HAWC2, the users manual. Tech. Rep. Risø-R-1597(ver.4-3)(EN), DTU Wind Energy, Roskilde, Denmark, April 2012.  The figure shows the displacement of the interface node for the full jacket model exposed to wave load compared with the response of the super element exposed the equivalent wave load. The match is almost perfect which indicates that the super element implementation in HAWC2 is valid. The figure shows the power spectrum of the axial force in one of the piles at mud level compared between the 3 methodologies. The high peaks at approx. 1.2 Hz  deviate between the models which is probably due to differerent damping ratios of the models. This need further investigation. Pile 4 Interface node 

Influence of foundation model complexity on the design loads for offshore WTG on jacket foundation

http://orbit.dtu.dk/ws/files/52282712/Influence_of_foundation_model_poster.pdf

Influence of foundation model complexity on the design loads for offshore WTG on jacket foundation

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology