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Universitetet i Stavangeruis.no
CFD of wind wave interactionsSiri M. Kalvig
Forskningsnettverket for miljvennlig energi
27.09.2016
StormGeo and the Norwegian Research Council for financing
NORCOWE
Supervisor group:
Bjrn Hjertager (UiS) main supervisor
Jasna B. Jakobasen (UiS)
Eirik Manger (Acona Flow Technology)
Nina Winther-Kaland (StormGeo)
Master students:
Richard Kverneland (UiS)
Anne Mette Nodeland (NTNU)
Tommy Fredriksen (Telemark University College)
Acknowledgement
Motivation and research question
Numerical wave simulations
Numerical turbine simulations
Wind tunnel test
Wave influenced wind turbine simulations (WIWiTS)
Conclusions and future perspectives
Outline
Motivation
Site specific offshore forecast Headquarter forecast office
Model set up in StormGeo
ECMWF
ERA-Interim
80km / 3 hours
StormGeo in-housemodeling1-9 km / 1 hourSWAN
We need better link between wave models and atmospheric models!
Illustration: Silje Kalvig stdahl
Atmospheric stratification and wave effects are two major factors affecting wind conditions over sea versus land.
Photo: Lene Eliassen
A gap between best knowledge and best practise ?
Yes!
Neutral stratification and a flat, smooth sea surface
are routinely used as assumptions in wind energy calculations.
Will wave influenced wind at an offshore wind site result in different wind shear and more turbulence than expected ?
And if so, how will this affect the turbines?
Research question
Illustration: Silje Kalvig stdahl
Method forwind turbine performance
and wake modeling
Testing, numerical experiments, produce
results
Summarize and conclude the PhD work
Couple the methods
Literature study, clarify the relevance for the PhD work
On wave-wind interactions and implications for offshore wind turbine
Testing, numerical experiments, produce
results
Method forwave influenced wind
simulations
Testing, numerical experiments, produce
results
From: Grand Valley State University
Need a new boundary condition that take into account the sinusoidal movement of the ground.
Numerical wave simulations
Different waves canbe superposed oneachother
, = 2(
) + 2(
)
is the total wave surface displacement, and are a unitvectors, x is the horizontal position at a given time t, a is the waveamplitude, is the wavelength and c is the wave speed.
Domain: 1200m x 25 m x 400 m, Logarithmic wind at inlet with U400m =8 m/s, z0=0.0002 m. Profiles are sampled from the middle of the domain (x=600 m) for every second between 251-300 seconds of simulations
Numerical wave simulations
wind aligned with wavewind oppose wavewithout wave
wind aligned with wavewind oppose wavewithout wave
Wave with a = 4 m, L = 50 m, c = 8.8 m/s Wave with a = 4 m, L = 100 m, c = 12.5 m/s
Domain: 1200m x 25 m x 400 m, Logarithmic wind at inlet with U400m =8 m/s, z0=0.0002 m. Profiles are sampled from the middle of the domain (x=600 m) for every second between 251-300 seconds of simulations
Numerical wave simulations
wind aligned with wavewind oppose wave
wind aligned with wavewind oppose wave
Wave with a = 4 m, L = 50 m, c = 8.8 m/s Wave with a = 4 m, L = 100 m, c = 12.5 m/s
Domain: 1200m x 25 m x 400 m, Logarithmic wind at inlet with U400m =8 m/s, z0=0.0002 m. Profiles are sampled from the middle of the domain (x=600 m) for every second between 251-300 seconds of simulations
Numerical wave simulations
wind aligned with wavewind oppose wave
wind aligned with wavewind oppose wave
Wave with a = 4 m, L = 50 m, c = 8.8 m/s Wave with a = 4 m, L = 100 m, c = 12.5 m/s
LES
URANS
Test with data from the NORCOWE & NOWITECH wind tunnel blind test.
Numerical turbine simulations
Testing of wind turbine models
Actuator disk model: openFOAMSteady state (simpleWindFoam)RANS, k-epsilon model1.7 million cells
Fully resolved method: ANSYS/FluentDone by Eirik Manger, Acona Flow technologyTransientRANS, k-omega model5.3 million cells
Actuator Line model: openFOAMTransient (pisoFoamTurbine)URANS, k-epsilon model2.4 million cells
Actuator line method in SOWFA
Actuator line method of Srensen and Shen1 used in the Simulator for Offshore Wind Farm Applications SOWFA2.
Manger and Kalvig visiting NREL, Boulder
1Srensen, J. N., & Shen, W. Z. (2002). Numerical modeling of wind turbine wakes. Journal of Fluids Engineering2Churchfield MJ, Lee S and Moriarty P 2012 Overview of the simulator for offshore wind farm application (SOWFA) National
Renewable Energy Laboratory, Golden, CO, USA 03 May 2012
Actuator line method, wind tunnel test
Waves + Actuator Line (SOWFA) FAST
Wave simulations are combined with the actuator line simulations of SOWFA and coupled with FAST. New set up: Wave Influenced Wind Turbine Simulations (WIWiTS)
New Method for direct study of:Wave Influenced Wind Turbine Simulations
WIWiTS
WIWiTS Using the NREL 5 MW turbine, reference turbine (hub height 90 m, rotor diameter 126 m)
WIWiTS
WIWiTS domain with wave aligned (left) with the wind direction and wave opposing the wind direction (right). The color contours showing the wind velocity in the x-direction.
WIWiTS
Generated rotor power per density (Wm3/kg) for the three different cases; wind and swell in the same direction (blue), wind and swell in the opposite direction (red) and wind over a surface with low roughness (black). L=100 m, a=4 m, c=12,5 m/s
wind aligned with wavewind oppose wavewithout wave
Inlet wind U400= 8m/s
WIWiTS with FAST
Stress at the blade root due to the flapwise bending moment at the blade root.Fatigue calculations by Lene Eliassen at NTNU.
Conclusions New method for wave induced wind simulations
The flow response over the waves is very different compared with flow over a flat sea surface.
Wave direction relative to wind direction important.
The swept wind turbine rotor area will be exposed to wind profiles and turbulent levels other than what is predicted with the usual assumption of a logarithmic wind profile and low turbulence levels over a flat surface.
URANS can serve as a good substitute to the more computational requiring LES for Actuator line (SOWFA) simulations.
The actuator line in SOWFA slightly improved (more robust)
Actuator line in URANS mode predict reasonably well both turbine performance and the turbine wake.
Conclusions
A new tool: Wave influenced wind turbine simulations WIWiTS.
Simulations with WIWiTS showed that swell will affect the power output. Oscillation in power had the same frequency as the waves. The opposed case gave slightly larger power output than the aligned case.
Simulations with WIWiTS coupled to FAST demonstrated that wave influenced wind increases the fatigue damage compared to a situation with no waves, especially for the cases where the wave field opposes the wind field.
Future perspectives
Further improvements of WIWiTS
WIWiTS with the FAST mode activated needs further validation and testing.
Only bottom fixed horizontal axis turbines are studied here. It would be interesting to extend the method to include vertical axis turbines and floating concepts.
Investigations on how knowledge from idealized CFD studies of wind wave effects can be incorporated in operational mesoscale models will also be an important area to explore.
Research Network for Sustainable Energy
Administration
Board
Energyefficiency
Renewabletechnology
Transition CCUS Smart cities
Mohsen Assadi Bjrn Hjertager Oluf Langhelle Ying Guo Chunming Rong
Future initiatives motivated from NORCOWE participation
Uis together with MARINTEK withsupport from:Statoil, Kongsberg, Fugro, NREL, Vestas, Von Karman Institute
WoW Project
Challenge:How can we model the effect the waves have on the MABL? And will the wave effect be significant for a the performance of a wind turbine?
Solutions:The dynamical behavior of the waves can be model be the use of a moving mesh approach in CFD and the wind turbine can be modeled by the actuator line method already developed in NRELs SOWFA.
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CFD of wind wave interactionsSlide Number 2Slide Number 3Slide Number 4Slide Number 5Slide Number 6Slide Number 7Slide Number 8Slide Number 9Slide Number 10Slide Number 11Slide Number 12Slide Number 13Slide Number 14Slide Number 15Slide Number 16Slide Number 17Slide Number 18Slide Number 19WIWiTSWIWiTSWIWiTS with FASTSlide Number 23Slide Number 24Slide Number 25Slide Number 26Slide Number 27Offgrid energy solution for fishfarmingMiljvennlig energy til fiskeoppdrettSlide Number 29Slide Number 30Floating VAWT, cost/benefit, upscalingWind energy in cold marine climateSlide Number 33Slide Number 34
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