Numerical Modeling of Offshore Support Structures and Approaches in Validation of Simulation Tools

Transcription

1 Numerical Modeling of Offshore Support Structures and Approaches in Validation of Simulation Tools Martin Kohlmeier, Wojciech Popko, Philipp Thomas Fraunhofer Institute for Wind Energy and Energy System Technology IWES 7. GIGAWIND Symposium, 2 March 2017, Leibniz Universität Hannover

2 Outline Motivation Aims and Scope within GIGAWIND life Research at Fraunhofer IWES Numerical Modeling and Virtual Experiments Large Scale Tests at the Test Center for Support Structures Analysis of Experimental Studies Validation of Simulation Tools Integral Modeling Tool The OC5 Project Current Status of Wind Turbine Code Validation First Verification Results Conclusion & Future Work Slide 2

3 Simulation and Validation in the framework of GIGAWIND life Overview of research objectives Simulation Framework Coupling of different simulation tools and approaches Data management and data analysis strategies Communication and integration of different tools and methods Implementation of Degradation Models Degradation of grout material, steel or soil and foundation structures Development of Tools and Programs Nonlinear and linear sea-state modeling and fluid-structure interaction Experiments and analysis of the design driving parameters Dynamics and Structural Design Solving of complex and coupled problems efficiently in time domain Verification & Validation of Programs & Models Slide 3

4 Fraunhofer IWES - Research with added value Slide 4

5 Fraunhofer IWES - Research with added value Work in GIGAWIND life: Integral Modeling Validation - of simulation modules - and structural components Experimental Data from Large Scale Tests at the Test Center for Support Structures in Hannover (TTH) Slide 5

6 Test Center for Support Structures Foundation Test Pit Empty foundation test pit 2014 After 3 rd time of sand preparation in September 2016 Foundation test pit in continuous operation from 2014 till 2017 Slide 6

7 Test Center for Support Structures Pile Installations Impact driven piles Vibratory driven piles Axially loaded piles (INNWIND.EU, 2015) Pile groups (TenneT, 2016) Impact driven piles (IRPWind, 2016) Shallow foundations Horizontally loaded piles subjected to different operational and environmental conditions (UnderwaterINSPECT, ) Horizontally loaded piles with degraded grouted connections (QS-M Grout, January 2017) Slide 7

8 Virtual Experiments - Motivation The design of experimental test set-ups and its optimization are essential to achieve accurate and reliable test results. Numerical simulations of large scale experiments can provide a virtual insight and are very promising for the definition of an optimum design of the experimental set-up, for gaining added value from detailed numerical investigations and may substitute additional tests. The range of application of a numerical model can be extended if it has a parameterized set-up of the entire model description and if an object oriented approach in mesh generation and simulation setup is applied, for example to easily analyse influences from boundaries affecting the behaviour of the interior domain Slide 8

9 Virtual Experiments - Example For lateral loading tests or dynamic structural analyses of for example a monopile a profound knowledge of both the static and dynamic behavior of the support structure and its foundation has to be evaluated in advance of a test campaign. Different finite element discretizations and model realizations are advantageous for different investigations, for example evaluation of the vibration characteristics, prediction of the pile bearing capacity or full analyses in time domain. Finite element discretization First tower bending mode Second tower bending mode Model development based on parameterized CAD models Parameter studies for finding the optimum test set-up Completion of experimental or measured test field data Slide 9

10 Virtual Experiments - Application Experimental test data from project UnderwaterINSPECT Static as well as dynamic experimental test set-up Realization of numerical models in Abaqus Optimization within GIGAWIND life Application of a an automated and script based model generation developed in Python language and applied in the finite element code Abaqus Comparison of experimental results for calibration and validation purposes Result: Reliable experimental test design based on validated numerical modeling Electrodynamic shaker (BD 10, Wölfel) mounted on a large scale monopile model with lateral loads applied by a hydraulic actuator (UnderwaterINSPECT, September 2015) Slide 10

11 Virtual Experiments - Application Experimental test data from project UnderwaterINSPECT Static as well as dynamic experimental test Realization of numerical models in Abaqus Optimization within GIGAWIND life Application of a an automated and script based model generation developed in Python language and applied in the finite element code Abaqus Comparison of experimental results for calibration and validation purposes Result: Reliable experimental test design based on validated numerical modeling Model realization: - Automated model set-up - Mohr-Coulomb material model - Soil-structure interaction: Friction contact between steel and soil - Installation procedure: wished in place Slide 11

12 Virtual Experiments Model Calibration Soil-structure interaction and material modeling Calibration of the soil material parameters Basis for validation against further test data about 15% deviation Model calibration Slide 12

13 Integral Modeling Model Set-up Fully coupled simulation model for (offshore) load assessment in time domain using the OneWind Modelica Library Aerodynamics unsteady aerodynamics blade element momentum theory (BEM) with dynamic stall and dynamic inflow generalized dynamic wake (GDW) with dynamic stall stochastic wind, IEC rd edition gust models Hydrodynamics Mac-Camy-Fuchs hydrodynamics, irregular waves (Pierson-Moskowitz und JONSWAP Spectra) Turbine control generic DLL interface (Bladed, Hawc2), build-in operating control Structural dynamics multi body approach Modal reduced anisotropic beam for blades and tower structure Offshore application: Euler-Bernoulli beam, Timoshenko beam under development Several offshore turbines available Monopile with IWES Wind Turbine IWT Spar, Tripod, Jacket, Semi-Submersible with NREL 5MW RWT IWES Wind Turbine IWT ess---media/iwes-wind-turbine-iwt html Slide 13

14 Integral Modeling - Verification Continuous verification of onshore turbine model against GH Bladed and NREL FAST good agreement, especially with Bladed Comparison with OC3 data for tripod substructure Results showing good agreement in phase and amplitude Next steps: Investigation of deviation in force components and adjustment structural damping Verification within OC5 Pahse III (jacket support structure) OC3 Tripod Slide 14

15 Validation of Simulation Tools Motivation Tools must continuously be verified and validated due to: Importance of the simulated loads (design, certification) New challenges for tools / new features of tools Objectives for validation activities: Assess simulation accuracy and reliability Investigate capabilities of implemented theories Refine applied analysis methods Train new analysts how to run tools correctly Identify further R&D needs Verification & Validation of OWT simulation tools in IEA OCX projects: Offshore Code Comparison Collaboration (OC3) Offshore Code Comparison Collaboration Continuation (OC4) Offshore Code Comparison Collaboration Continuation with Correlation (OC5) Source: National Renewable Energy Laboratory, USA focused on verifying offshore wind modeling tools through code-to-code comparisons focuses on validating the tools through code-to-data comparisons Slide 15

16 Validation of Simulation Tools OC5 Phase III Phase I Monopile Tank Testing 01/ /2015 Phase II Semi submersible Tank Testing 01/ /2016 Phase III Full-scale open ocean system 01/ /2018 Slide 16

17 Validation of Simulation Tools OC5 Phase III 34 participants 13 countries 3 continents Slide 17

18 Validation of Simulation Tools OC5 Phase III Senvion (Germany) provided data to setup the turbine and the tower models with all necessary control settings that might allow running benchmark exercises on validation of simulation tools. OWEC Tower (Norway) will provide design data of the jacket substructure, including its foundation and the transition piece. Source: er_5m_423cd32f6c.png Slide 18

19 Validation of Simulation Tools OC5 Phase III A numerical model of the REpower 5M wind turbine is setup by OC5 Phase III participants. It is based on the simplified structural data of the REpower 5M turbine that were provided by Senvion. Before its Validation against the fullscale measurement, its basic Verification has to be performed against a detailed turbine model available at SWE at the University of Stuttgart. The SWE model includes: detailed description of the entire OWT including structural and aerodynamic properties of LM Wind Power blades, fully functional controller from Senvion. Source: er_5m_423cd32f6c.png Slide 19

20 OC5 Phase III Verification Results Fore-aft My at tower bottom [knm] First exemplary verification results Check of static forces and moments at the tower bottom Tower and RNA mass [t] Slide 20

21 OC5 Phase III Verification Results First exemplary verification results Rigid turbine, power production check of tuned controller parameters with deterministic stepped wind changing from V cut-in = 3 m/s to V cut-out = 30 m/s, with a constant step of 1 m/s lasting for 50 s Generator power plots GenPower [kw] S - ASHES 3000 EDF - Fast 8 IWES - Bladed 4.7 MARINTEK - Riflex 2000 NREL - Fast 8 SWE - Flex UoU - Fast 8 WEIT - Fast Time [s] Slide 21

22 OC5 Phase III Verification Results First exemplary verification results Rigid turbine, power production check of tuned controller parameters with deterministic stepped wind changing from V cut-in = 3 m/s to V cut-out = 30 m/s, with a constant step of 1 m/s lasting for 50 s Pitch angle plot Differences in blade aerodynamics reflected in pitch angle between rated and 14 m/s - > lower pitch for SWE turbine between 15 and 17 m/s -> SWE and other codes match well above 18 m/s -> higher pitch angle for SWE turbine PitchAngle [deg] S - ASHES EDF - Fast 8 IWES - Bladed MARINTEK - Riflex NREL - Fast 8 SWE - Flex5 5 UoU - Fast 8 WEIT - Fast Time [s] Slide 22

23 Conclusion and Future Work The scope of work within GIGAWIND life Validation of numerical models against experimental data of large scale tests Development and application of modeling tools Findings Sub model development is effective within integral modeling tools The assessment of OWT simulation tools should consider field measurement data Ongoing work The validation against alpha ventus windfarm data has started with verification of turbine models Future Work Further activities within the project OC5 Phase III Application of the data management tool might be very attractive in case of large amounts of data to cope with Slide 23

24 Thank you very much for your attention! Wojciech Popko (Leader of OC5 III): Martin Kohlmeier: Slide 24