Offshore Code Comparison Collaboration: Phase III Results Regarding Tripod Support Structure Modeling

This work presents the results of a benchmark study on aero-servo-hydro-elastic codes for offshore wind turbine dynamic simulation. The codes verified herein account for the coupled dynamic systems including the wind inflow, aerodynamics, elasticity and controls of the turbine, along with the incident waves, sea current, hydrodynamics and foundation dynamics of the support structure. A large set of time series simulation results such as turbine operational characteristics, external conditions, and load and displacement outputs was compared and interpreted. Load cases were defined and run with increasing complexity to trace back differences in simulation results to the underlying error sources. This led to a deeper understanding of the underlying physical systems. In four subsequent phases-dealing with a 5-MW turbine on a monopile with a fixed foundation, a monopile with a flexible foundation, a tripod and a floating spar buoy-the latest support structure developments in the offshore wind energy industry are covered, and an adaptation of the codes to those developments was initiated. The comparisons, in general, agreed quite well. Differences existed among the predictions were traced back to differences in the model fidelity, aerodynamic implementation, hydrodynamic load discretization and numerical difficulties within the codes. The comparisons resulted in a more thorough understanding of the modeling techniques and better knowledge of when various approximations are not valid. More importantly, the lessons learned from this exercise have been used to further develop and improve the codes of the participants and increase the confidence in the codes' accuracy and the correctness of the results, hence improving the standard of offshore wind turbine modeling and simulation. One purpose of this paper is to summarize the lessons learned and present results that code developers can compare to. The set of benchmark load cases defined and simulated during the course of this project-the raw data for this paper-is available to the offshore wind turbine simulation community and is already being used for testing newly developed software tools. Despite that no measurements are included, the large number of participants and the-in general-very fine level of agreement indicate high trustworthy results within the physical assumptions of the codes and the simulation cases chosen. Other cases, such as large prebend flexible blades, large wind shear, large yaw error or transient maneuvers, may not show the same level of agreement. These cases were deliberately left out because the focus is on the specific offshore application. Further on, this benchmark study includes participating codes and organizations by name (contrary to several previous benchmark studies) that gives the reader a chance to find results from one particular code of interest

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“…More details may be found in Passon et al ., Jonkman et al ., Nichols et al . and Jonkman et al . (phases I–IV, respectively).…”

Section: Results From Code‐to‐code Comparisonsmentioning

confidence: 82%

“…The three pile sleeves of the tripod were cantilevered at mudline, and the hub height of the turbine over MSL was kept the same (see Nichols et al . for more details on the tripod).…”

Section: Modeling Inputmentioning

confidence: 99%

Verification of aero‐elastic offshore wind turbine design codes under IEA Wind Task XXIII

et al. 2013

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“…Thus, the presented model can be used as a simple tool for elaborating new research topics and different or innovative wind turbine system designs. This flexibility of model adaption is demonstrated on the example of the OC4 semi-submersible platform (Robertson et al, 2014), the OC3 tripod (Nichols et al, 2009), and the OC4 jacket (Jonkman et al, 2012), shown in Figures 9(a), 9(b), and 9(c), respectively. Furthermore, Table 3 compares the complexity of those models, using the same statistics from Dymola as presented in Table 1 for the spar-buoy floating wind turbine model.…”

Section: Model Adaptionmentioning

confidence: 95%

The OneWind Modelica Library for Floating Offshore Wind Turbine Simulations with Flexible Structures

Leimeister

Thomas

2017

Linköping Electronic Conference Proceedings

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Floating offshore wind turbines are getting more and more into the focus of interest, as industries aim for larger turbines and deeper water areas. Fully coupled analyses of those highly complex systems are challenging. In this paper, the hierarchical programming structure in Modelica is used to model a fully flexible floating wind turbine system. The single components, as well as special difficulties that have to be dealt with during modeling, are addressed. On basis of a reference floating offshore wind turbine, the implemented fully flexible model is compared with its rigid equivalent, as well as results from code-to-code comparisons of free-decay simulations. The findings are satisfactory and confirm the theoretical assumptions. In addition, further applications of the created model are shown.

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“…Therefore, wind turbine computer-aided engineering (CAE) tools need to take a system approach for predicting aerodynamic and hydrodynamic loads throughout the support structure, rotor, and drive train components. Large international code com parison efforts [1][2][3] have helped to push forward the development of such CAE tools (i.e., wind turbine design codes). In this context, the aero-hydro-servo-elastic tool FAST 4 , developed at the National Renewable Energy Laboratory (NREL), has been reformulated to enhance its development flexibility and capabilities to model multiple physics do mains with different levels of fidelity.…”

Section: Introduction: Fast Modularization Frameworkmentioning

confidence: 99%

Verification of the new FAST v8 Capabilities for the Modeling of Fixed-Bottom Offshore Wind Turbines

Barahona

Jonkman

Damiani

et al. 2015

33rd Wind Energy Symposium

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Offshore Code Comparison Collaboration: Phase III Results Regarding Tripod Support Structure Modeling

Cited by 6 publications

References 1 publication

Verification of aero‐elastic offshore wind turbine design codes under IEA Wind Task XXIII

Verification of aero‐elastic offshore wind turbine design codes under IEA Wind Task XXIII

The OneWind Modelica Library for Floating Offshore Wind Turbine Simulations with Flexible Structures

Verification of the new FAST v8 Capabilities for the Modeling of Fixed-Bottom Offshore Wind Turbines

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