Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Smooth hill validation in FUROW’s windresource module using OpenFOAM

5th Symposium on OpenFOAM in Wind Energy(SOWE 2017)

Elliott Bache, Javier Magdalena Saiz, Jose Marın Palacios,Jesus Matesanz Garcıa and Laura Cano Criado

SOLUTE Ingenieros, Avda. Cerro del guila 3, 28703 - San Sebastin de losReyes (Madrid)

April 27th, 2017

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Solute Ingenieros

RailwayAuto space Energy Civil engineering

Wind & renewable

energies

Activities in the following fields:

• Structural & mechanical analysis

• Advanced numerical simulation

• Wind turbine load analysis and dynamics

• Wind turbine certification

• Engineering & design of wind energyprojects

• SODAR & mast measurement campaign

• Wind resource evaluation & micro-siting

• Techno-economic viability studies

• Software development

• R&D projects

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

For Uncertainty Reduction Of Wind

Data analysis

• Download ofMERRA, MERRA2& ERA-I data

• Manual flagging &flagging with rules

• MCP analysis withseveral referencemasts

Micrositing

• Wake modelingusing up to 8 wakemodels

• Site compliance tocheck class andsubclass for eachposition of the windfarm

Wind resource assessment

• Wind resourcecalculation usingmultiple masts

• Extreme wind maps

• Use of atmosphericstability parameters insimulations

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

FUROW’s linear wind flow model

1Jackson, P.S. and Hunt, J.C.R. (1975), Turbulent wind flow over a low hill,

J. Royal Met. Soc. 101, pp 929-955.

Model derived from UPMORO code & based on Jackson & Hunt(1975)1potential flow theory

• As is WAsP

• Atmospheric stability is modified through Monin-Obukhovlength

• Forests are modelled with canopy heights and forest density

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

OpenFOAM implementationin FUROW

• For more complex terrains, moreprecise (& longer) simulations arenecessary

• Linear calculation is used toinitialize & impose BC’s forReynolds-averaged Navier-Stokes(RANS) simulations

(Source: Backpacker magazine,Image by Mark Goodreau)

40m 80m 120m

Wind Wind Wind

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

OpenFOAM implementationin FUROW

Linear solution mappedto CFD domain

OpenFOAM solution

40m 80m 120m

Wind Wind Wind

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Wind tunnel model

2G. Byun, R.L. Simpson, C. Long, AIAA journal 42,754 (2004)

OpenFOAM model is validated with experimental results2

• Wind tunnel experiment with bump

• Inlet velocity = 27.5 m/s

• Recirculation bubble & velocity profiles downstream ofbump are compared

0 0.2 0.4 0.6 0.8 110

−3

10−2

10−1

100

z/H

[−

]

U/Uref

k/kref

x

zy

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

RANS Turbulence models

Different turbulence models are used

• High Re Spalart-Allmaras

• Low Re Spalart-Allmaras

• High Re k-ε

• Low Re Launder Sharma k-ε

• Low Re Lien Leschziner k-ε

• High Re k-ω

• Low Re k-ω

• High Re k-ω SST

• Low Re k-ω SST

Inlet conditions

l = 0.22δ

ε =C

3/4µ k3/2

l

ω =ε

Cµk

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Separation (a) & reattachment (b) pts.

2G. Byun, R.L. Simpson, C. Long, AIAA journal 42,754 (2004)3LL = Lien Leschziner, LS = Launder Sharma, SA = Spalart-Allmaras

Experimental results2

Model Pt. a Pt. b

Experimental 2 0.97 2.00High Re k-ε - -Low Re LL3k-ε 0.64 2.05Low Re LS3 k-ε 0.96 1.92High Re SA3 - -Low Re SA3 0.32 2.24High Re SST 1.15 1.92Low Re SST 0.192 2.12High Re k-ω 1.28 1.99Low Re k-ω 0.51 1.99

→ High Re k-ε & SA3 have no bubble!

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Downstream velocity profiles :far from wall

2G. Byun, R.L. Simpson, C. Long, AIAA journal 42,754 (2004)3LL = Lien Leschziner, LS = Launder Sharma, SA = Spalart-Allmaras

Velocity profiles reported at x/H = 3.63 downstream ofbumptop2,3

0 0.2 0.4 0.6 0.8 10

0.2

0.4

0.6

0.8

1

U/Uref

[−]

z/H

[−

]

Experimental

High Re k−ε

Low Re LL k−ε

Low Re LS k−ε

High Re SA

Low Re SA

High Re SST

Low Re SST

High Re k−ω

Low Re k−ω

Best resultsLow Re k-ω

Worst resultsLow Re SSTHigh Re SALow Re SA

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Downstream velocity profiles :near wall

2G. Byun, R.L. Simpson, C. Long, AIAA journal 42,754 (2004)3LL = Lien Leschziner, LS = Launder Sharma, SA = Spalart-Allmaras

Velocity profiles reported at x/H = 3.63 downstream ofbumptop2,3

0 0.2 0.4 0.6 0.8 110

−4

10−3

10−2

10−1

100

U/Uref

[−]

z/H

[−

]

Experimental

High Re k−ε

Low Re LL k−ε

Low Re LS k−ε

High Re SA

Low Re SA

High Re SST

Low Re SST

High Re k−ω

Low Re k−ω

Best resultsLow Re k-ω

Worst resultsHigh Re k-ωHigh Re SALow Re SA

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Two-bump domain

Two-bump domain is created to study bubble effect on 2nd

bump

Large dispersion in results at2nd bumptop

⇒ Turbulence model cangreatly affect windresource in complexterrain!

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

1st bumptop velocity profiles

3LL = Lien Leschziner, LS = Launder Sharma, SA = Spalart-Allmaras

All profiles3 follow similar (more or less) tendency

0.8 1 1.2 1.41

1.2

1.4

1.6

1.8

2

U/Uref

[−]

z/H

[−

]

High Re k−ε

Low Re LL k−ε

Low Re LS k−ε

High Re SA

Low Re SA

High Re SST

Low Re SST

High Re k−ω

Low Re k−ω

No bubbleHigh Re k-εHigh Re SA

Deformed bubbleLow Re SALow Re SST

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

2nd bumptop velocity profiles

3LL = Lien Leschziner, LS = Launder Sharma, SA = Spalart-Allmaras

Bubble has large effect on 2nd bumptop profiles3

• Standard deviation (σ) is much larger

• Height at which σ ≤ 2.5% (excluding deformed bubblemodels) :

• 1st bumptop : ≈ 0.15H• 2nd bumptop : ≈ 0.30H

0.8 1 1.2 1.41

1.2

1.4

1.6

1.8

2

U/Uref

[−]

z/H

[−

]

High Re k−ε

Low Re LL k−ε

Low Re LS k−ε

High Re SA

Low Re SA

High Re SST

Low Re SST

High Re k−ω

Low Re k−ω

0 0.02 0.04 0.06 0.081

1.2

1.4

1.6

1.8

2

σU/U

ref

[−]

z/H

[−

]

1st

bump

2nd

bump

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Conclusions

One bump in wind tunnel

• No bubble : High Re k-ε & Spalart-Allmaras

• Velocity profile downstream of bubble

• Closest to experiment : Low Re k-ω• Furthest from experiment : Spalart-Allmaras (high

& low Re)

Two bumps

• Dispersion at 2nd bumptop is much larger than at 1st

• Larger bubble makes more diffuse boundary layerdownstream• For a 200m hill, 5% differences may occur up to

60m at 2nd hilltop

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

Future work

Current studies

• Periodic hills case

• Full-scale domain

• Detached eddy simulation (DES)

Future studies

• Large eddy simulation (LES)

• Modify wall functions

• More complex• Function of p+

Hill validationin OpenFOAM

for FUROW

Elliott Bache

Solute

FUROW

Wind flow model

OpenFOAMImplementation

Validationmodel

Wind tunnel

Numerical model

Results

One bump

Two bumps

Conclusions

The End

Thank you!

Any questions?

Any comments?

elliott.bache@solute.es