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Validation of a CFD model with a triple-lidar system upstream of a wind turbine incomplex terrain

Meyer Forsting, Alexander Raul; Troldborg, Niels; Bechmann, Andreas; Angelou, Nikolas; Vasiljevic,Nikola

Publication date:2016

Document VersionPeer reviewed version

Link back to DTU Orbit

Citation (APA):Meyer Forsting, A. R. (Author), Troldborg, N. (Author), Bechmann, A. (Author), Angelou, N. (Author), &Vasiljevic, N. (Author). (2016). Validation of a CFD model with a triple-lidar system upstream of a wind turbine incomplex terrain. Sound/Visual production (digital)

https://orbit.dtu.dk/en/publications/6be20a57-eb4d-420e-bcd4-e5013370db5c

Validation of a CFD model with a triple-lidarsystem upstream of a wind turbine in complex

terrain

Alexander Meyer Forsting, Niels Troldborg, Andreas Bechmann, Nikolas Angelou,

Nikola Vasiljevic

DTU Wind Energy, Technical University of Denmark

Overview

• The induction zone

• Power curve measurements

• Computational method

• CFD simulations

• Triple-lidar measurements in the induction zone

• CFD – measurement comparison

• Conclusion

• Future work

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The induction zone

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Distance from WT

D

Velo

cit

y


The induction zone

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Distance from WT

D

Velo

cit

y

Thrust


Power curve measurements

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Distance from WT

D

Velo

cit

y

2.5 D



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Distance from WT

D

Velo

cit

y

2.5 D 0.5 D



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D

Velo

cit

y

2.5 D 0.5 D Distance from WT



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D

Velo

cit

y

2.5 D 0.5 D Distance from WT

Induction zone model • Predict uncertainty

• Capture thrust dependency


Power curve measurementsin complex terrain

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h

h


Power curve measurementsin complex terrain

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h

h


Modeling the induction zone in complex terrain

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Wake

Separation

Multi-scale

turbulence

DTU Wind Energy, Technical University of Denmark13 15/06/2016

General

• Multi-purpose finite volume solver

• Block-structured grid with collocated variables

• Highly parallelised

• Body forces are implemented via modified

Rhie-Chow algorithm

Complex terrain

• Steady-state incompressible RANS

• QUICK scheme solved convective terms

• SIMPLE the pressure-linked terms

EllipSys3D



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Multi-scale

turbulence

𝒌 − 𝜺 − 𝒇𝒑 turbulence model



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𝑧0

𝑧

𝑈



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• Neutral stratification

• No Coriolis

Terrain flow becomes Reynolds number independent



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Actuator disc representation of WT

• Permeable disc with body forces

• Intersectional grid determines forces

in fluid domain

• Either constant thrust coefficient over disc

• Or 2-D airfoil data


Complex terrain test case: Perdigão

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Terrain treatment for mesh generation

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Far-field terrain and reference roughness

• Smoothed over grid spacing and

towards the edges of the domain


The domain

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17 km


The domain

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Grid sensitivity

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Δ𝑥 =𝑅

16= 2.56 𝑚 2.13𝑀 𝑐𝑒𝑙𝑙𝑠


Measurements at Perdigão

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• Synchronised lidar measurements around WT and valley


Measurements at Perdigão

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Synchronised triple-lidar


CFD Results

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21

8°

26

3°


CFD Results

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218°

263°

Wind directions


Triple-lidar results

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By R. Menke


Comparaison triple-lidar and CFD

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1.6 R

2.6 R



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16 m


Conclusion

• Automated complex terrain simulations incorporating several pre-

processing steps

• Triple-lidar shows high potential for complex flow measurements

• Large uncertainty in inflow conditions needs to be accounted for

• Steady-state RANS seems to capture induction zone correctly

• Computational uncertainty from:

– Stratification

– Roughness

– Turbine

– Terrain

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Future work

• Investigate more measurement periods

• Include variability of wind direction into validation methodology

• Include stratification

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Thanks for your attention!

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Questions?

validation of a cfd model with a triple-lidar system upstream ......complex terrain test case:...

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