aerodynamic design of a high solidity canted vertical axis ... · pdf filefirst symposium on...
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1 Ariane FrèreEnergy & Buildings Team
Contacts:[email protected]. ref.: D4WIND-NS-010-00
First Symposium on OpenFOAMⓇ in Wind Energy20th & 21st of March 2013 - Oldenburg
Aerodynamic design of a high solidity canted Vertical Axis Wind Turbine with OpenFOAM
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© 2013 Cenaero – All rights reserved
1/ Project Introduction
OpenFOAM interest for VAWT design
Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
Implicit Large Eddy SimulationCenaero in-house tool:
Argo DGM
Dynamic polars: CL for various TSR [3]
D4Wind Project :
• Walloon Region funds
• 1 SME, 1 university & 1 research center
• Task 1: Aerodynamics rotor design
Vertical Axis Wind Turbines:
• High & varying AOAs
• Highly unsteady flow, more complex than HAWT
• Difficulty to find accurate polar (dynamic stall)
Strong interest in unsteady CFD:
• Airfoils � static & dynamic polars
• Full rotor structure � arms, attachment… effects on performance & acoustic
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11/ Project Introduction
Presentation of the 2D validation case
Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
Experimental set-up for the straight (left VAWT) and canted (right) VAWT [1] (naca0015, chord 0.420m, rotor diameter 2.8m, height 2.9m)
© 2013 Cenaero – All rights reserved
Project steps:
• Validate CFD approach using OpenFOAMtools on 2D cases
• Compare 2D to 3D (straight blades)
• Study the canted effect
• Use developed methodology for D4Wind
Set-up:
• Meshing Gambit/ANSYS
• Transient, incompressible, unsteady flows with dynamic mesh: pimpleDyMFoam
• 2D URANS with turbulence models: k-ε & k-ω SST
• Δt as Courant number ≤ 0.9
• Naca0015, 0.420m chord, 2.8 rotor diameter, 0.1m axis diameter, no pitch
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Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
2/ Modelling Approach
Mesh & boundary conditions
Mesh specification:
• Unstructured triangular mesh
• Specification:
• Domain: 14φ*21φ (φ=2.8m)
• Rotating disk: 4φ
• 2D mesh extruded
• Blades first cell as y+ ≤200
• Max aspect ratio 1.2
Operating conditions:
• Inlet velocity: U=10m/s
• Turbulence intensity 10%
• AMI rotation 30:140 RPM (Re 4:8e5)
© 2013 Cenaero – All rights reserved
Inletv=constant
dp/dy=0
Symmetry
cyclicAMI
movingWallWallFunction
Outletp=constant
dv/dy=0
Symmetry
movingWallWallFunction
Top&Bottom: empty
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Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
2/ Modelling Approach
Mesh dependence study
• 50k nodes mesh chosen (vs. 150k in reference [2])
• Further analysis: 220k nodes
© 2013 Cenaero – All rights reserved
Simulations & ref. data [2] at TSR 1.32, U=10m/s, k- ω SST (k=1.5, ω=5.6), third revolution of blade n°2
Nodes Run time(3*360°)
Cp (exp:0.23)
20k 40 CPUh 0.09
50k 420 CPUh 0.20
110k 1200 CPUh 0.20
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Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
2/ Modelling Approach
Turbulence sensitivity study
© 2013 Cenaero – All rights reserved
Simulations at TSR 1.2, U=10m/s, 50knodes mesh, third revolution of blade n°2
• k- ω SST chosen for the present study (as in reference [2])
• Turbulence level doesn’t alter much the results
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Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
3/ Result & Discussion
Vorticity TSR 1.32
TSR 1.32, U=10m/s, k- ω SST (k=1.5, ω=5.6) 50k nodes mesh
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Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
3/ Result & Discussion
Vorticity TSR 0.4
TSR 0.4, U=10m/s, k- ω SST (k=1.5, ω=5.6) 50k nodes mesh
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Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
4/ Results & Discussion
Thrust force coefficient variation with θ for 4 TSR
© 2013 Cenaero – All rights reserved
TSR 0.4
TSR 1.32
TSR 0.7
TSR 1.81
Simulations at U=10m/s, k- ω SST (k=1.5, ω=5.6), third revolution of blade n°2, 50k nodes mesh
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Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
4/ Results & Discussion
Cp curve compared to reference numerical & experimental results
© 2013 Cenaero – All rights reserved
Red dots=openFoam results with U=10m/s, k- ω SST (k=1.5, ω=5.6) 50k nodes mesh: TSR=0.4 Cp=0.03,
TSR=0.7 Cp=0.05, TSR=1.2 Cp= 0.16, TSR=1.32 Cp=0.20, TSR=1.81 Cp=0.29
Fig
ure
6.11
from
[2]
v
v
• 2D analysis shows good agreement with the reference
• Further analysis required in [1.5:2] TSR region
v
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Conclusions:
• 2D comparison to benchmark shows very encouraging results
• Mesh 50k converges in reasonable time
• k-ω SST well adapted for VAWT highly separated flow
Perspectives:
• Mesh dependency & numerical schemes need to be further analysed
• Methodology to reduce computational time for 3D cases:
• Change mesh: tetrahedral to hexahedral
• Improve parallelisation approach
• Steps with different numerical schemes
• … ?
Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg
5/ Conclusion and Perspectives
Accuracy vs. computational time
© 2013 Cenaero – All rights reserved
3D simulations: extrusion (top) & full 3D (bottom) (Naca0015 chord
0.420, V10m/s, TSR 1.2 )
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Thank you for your attention!
Symposium on OpenFOAM in Wind Energy 21/03/2013 - Oldenburg © 2013 Cenaero – All rights reserved
References:
[1] Armstrong S., Fiedler A., Tullis S., Flow separation on a high Reynolds number, high solidity vertical axis wind turbine with straight and canted
blades and canted blades with fences, Renewable Energy, Elsevier, May 2012
[2] McLaren K., A numerical and experimental study of unstedy loading of high solidity vertical axis win turbines, Open Access Dissertations and
Theses McMaster University, Paper 6091, http://digitalcommons.mcmaster.ca/opendissertations/6091
[3] Mukinovic M., Brenner G., Rahimi A., Analysis of Vertical Axis Wind Turbines, New Results in Numerical and Experimental Fluid Mechanics VII
Notes on Numerical Fluid Mechanics and Multidisciplinary Design, Volume 112, 2010, pp 587-594
Questions?
Comments?
TSR 0.4, U=10m/s, k- ω SST (k=1.5, ω=5.6) 50k nodes mesh(video at 1/10 rate)