1. CFD Modeling of Vertical Axis Wind Turbine
Ali S. Alhamaly
Mechanical Engineering
May 4, 2016

2. Introduction about
wind turbine
Description of the problem
Results of the simulation
This presentation focuses on presenting the results of CFD
simulation of vertical axis wind turbine
2

3. 3
Introduction about Wind Turbine
1

4. Wind turbines are divided into two categories: horizontal axis
and vertical axis
HAWT: axis of rotation
parallel to the wind
VAWT: axis of rotation
perpendicular to the wind

5. Wind turbines extract energy by utilizing aerodynamic forces
that are projected in the direction of rotation
Wind blowing
Drag
Lift
Airfoil (wing section)

6. 6
Description of the Problem
2

7. The problem is to simulated the flow of wind turbine by taking
2D sectional cut of the a straight bladed 3D VAWT
Generic 3D turbine
2D geometry is simulated that
captures the essential physics
Looking from top

8. The computational domain has rotating and stationary
regions separated by sliding interface
1: Velocity inlet
2: Pressure outlet
3: Sliding interface
4: NACA-0015
4
4
3
1
7D3D
2
20D
1.25D
V = 12 m/s
Rotation = 115 RPM
D= 4m
Chord = .6 m

9. Unstructured triangular mesh is used throughout the
computational domain
Rotating zone mesh

10. Unstructured triangular mesh is used throughout the
computational domain
Airfoil mesh

11. Unstructured triangular mesh is used throughout the
computational domain
Stationary zone mesh

12. 12
Results of the Simulation
3

13. Grid Independence has been assessed using four different
meshes
Mesh # # Element on
boundary1
# Element on
boundary2
# Element on
boundary3
# Element on
boundary4
Total Elements
1 60 60 80 100 60490
2 60 60 160 160 134616
3 60 60 240 240 262014
4 60 60 240 300 338172
4
4
3
1
2

14. Turbine torque is changing with mesh refinement but mesh 3
and mesh 4 shows very similar values

15. Turbine torque is changing with mesh refinement but mesh 3
and mesh 4 shows very similar values

16. Turbine torque does not change with time step refinement
indicating 1 degree per time step is enough

17. Validation shows that CFD simulation captures the essential time
variation of torque and gives averaged torque with error less than 9%

18. Tangential force result shows that the forces are different in
the upwind and downwind portion
Reference
𝜃
𝑛
𝑡
Tangential force
Coefficient for one blade

19. Mean torque is greatly reduced from the peak torque value
Reference
𝜃
𝑛
𝑡
Torque coefficient
for whole turbine

20. Velocity magnitude contour shows the wake of the turbine
𝜃 = 0 𝑜

21. Vorticity field contour shows the wake of the turbine
𝜃 = 0 𝑜

22. Incoming wind speed is reduced by .5 m/s for each turbine
rotation

23. Reducing the wind speed has the effect of reducing the peak
force but does not alter the time variation significantly
Reference
𝜃
𝑛
𝑡

24. Mean torque is reduced by 7% in variable wind compares with
constant wind condition
Reference
𝜃
𝑛
𝑡

25. Introduction about
wind turbine
Description of the problem
Results of the simulation
In conclusion, CFD simulation of vertical axis wind turbine
has been successfully conducted
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