numerical modeling of offshore support structures and ... · numerical modeling of offshore support...

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

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


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


Fraunhofer IWES - Research with added value


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


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


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


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


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


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


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“


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


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


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


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


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



34 participants 13 countries 3 continents



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


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


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]


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


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


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


Thank you very much for your attention!

Wojciech Popko (Leader of OC5 III): [email protected] Martin Kohlmeier: [email protected]

www.gigawind.de

numerical modeling of offshore support structures and ... · numerical modeling of offshore support...

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