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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
Slide 2
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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 3
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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 4
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Fraunhofer IWES - Research with added value
Slide 5
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Fraunhofer IWES - Research with added value
Experimental Data from Large Scale Tests at the Test Center for Support Structures in Hannover (TTH)
Work in GIGAWIND life: Integral Modeling Validation - of simulation modules - and structural components
Slide 6
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Test Center for Support Structures Foundation Test Pit
Empty foundation test pit 2014
Foundation test pit in continuous operation from 2014 till 2017
After 3rd time of sand preparation in September 2016
Slide 7
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Test Center for Support Structures – Pile Installations Impact driven piles
Shallow foundations
Axially loaded piles (INNWIND.EU, 2015)
Pile groups (TenneT, 2016)
Horizontally loaded piles subjected to different operational and environmental conditions (UnderwaterINSPECT, 2012-2015)
Impact driven piles (IRPWind, 2016)
Horizontally loaded piles with degraded grouted connections (QS-M Grout, January 2017)
Vibratory driven piles
Slide 8
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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
Virtual Experiments - Motivation
Slide 9
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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.
Model development based on parameterized CAD models Parameter studies for finding the optimum test set-up Completion of experimental or measured test field data
Finite element discretization
First tower bending mode
Second tower bending mode
Virtual Experiments - Example
Slide 10
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Electrodynamic shaker (BD 10, Wölfel) mounted on a large scale monopile model with lateral
loads applied by a hydraulic actuator (UnderwaterINSPECT, September 2015)
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
Slide 11
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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
Virtual Experiments - Application
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 12
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Soil-structure interaction and material modeling Calibration of the soil material parameters Basis for validation against further test data
Model calibration
Virtual Experiments – Model Calibration
about 15% deviation
Slide 13
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Integral Modeling – Model Set-up
http://www.windenergie.iwes.fraunhofer.de/en/press---media/iwes-wind-turbine-iwt-7-5-164.html
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, IEC61400-1 3rd 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-7.5-164 Spar, Tripod, Jacket, Semi-Submersible with NREL 5MW RWT
IWES Wind Turbine IWT-7.5-164
Slide 14
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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
Next steps: Investigation of deviation in force components and adjustment structural damping Verification within OC5 Pahse III (jacket support structure) OC3 Tripod
Results showing good agreement in phase and amplitude
Slide 15
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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)
focused on verifying offshore wind modeling tools through code-to-code comparisons focuses on validating the tools through code-to-data comparisons
Source: National Renewable Energy Laboratory, USA
Slide 16
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Validation of Simulation Tools – OC5 Phase III
Phase I Monopile – Tank Testing
01/2014 – 05/2015
Phase II Semi submersible –
Tank Testing 01/2015 – 12/2016
Phase III Full-scale open ocean system
01/2017 – 05/2018
Slide 17
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Validation of Simulation Tools – OC5 Phase III
34 participants 13 countries 3 continents
Slide 18
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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 sub-structure, including its foundation and the transition piece.
Source: https://www.alpha-ventus.de/fileadmin/_processed_/csm_av_repower_5m_423cd32f6c.png
Slide 19
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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 full-scale 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: https://www.alpha-ventus.de/fileadmin/_processed_/csm_av_repower_5m_423cd32f6c.png
Slide 20
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
OC5 Phase III – Verification Results First exemplary verification results Check of static forces and moments at
the tower bottom.
475
500
525
550
575
600
625
650
675
Tow
er a
nd
RN
A m
ass
[t]
-5400
-5200
-5000
-4800
-4600
-4400
-4200
-4000
Fore
-aft
My
at t
ow
er b
ott
om
[kN
m]
Slide 21
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
First exemplary verification results Rigid turbine, power production –
check of tuned controller parameters with deterministic stepped wind changing from Vcut-in = 3 m/s to Vcut-out= 30 m/s, with a constant step of 1 m/s lasting for 50 s
Generator power plots
0 100 200 300 400 500 600 700
Time [s]
0
1000
2000
3000
4000
5000
6000
Gen
Pow
er [k
W]
4S - ASHES
EDF - Fast 8
IWES - Bladed 4.7
MARINTEK - Riflex
NREL - Fast 8
SWE - Flex5
UoU - Fast 8
WEIT - Fast 8
OC5 Phase III – Verification Results
Slide 22
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
First exemplary verification results Rigid turbine, power production –
check of tuned controller parameters with deterministic stepped wind changing from Vcut-in = 3 m/s to Vcut-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
400 500 600 700 800 900 1000 1100 1200 1300 1400
Time [s]
0
5
10
15
20
25
30
Pitc
hAng
le [d
eg]
4S - ASHES
EDF - Fast 8
IWES - Bladed 4.7
MARINTEK - Riflex
NREL - Fast 8
SWE - Flex5
UoU - Fast 8
WEIT - Fast 8
OC5 Phase III – Verification Results
Slide 23
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
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
Conclusion and Future Work
Slide 24
Dr. Martin Kohlmeier, GIGAWIND life Symposium, March 2nd, 2017
Thank you very much for your attention!
Wojciech Popko (Leader of OC5 III): [email protected] Martin Kohlmeier: [email protected]
www.gigawind.de