2. Presentation Outline
• Motivation
• Why VAWT
• Issues address in present work
• Objective
• Why OpenFOAM
• OpenFOAM Utility and its capabilities
• Case Setup
• Mesh Validation
• Case Validation
• Results and Discussion.
• Conclusion.
2
3. Motivation
• Google, Facebook, IKEA, Microsoft and Starbucks are also investing in wind energy as
a hedge against the unpredictability of fossil fuel price fluctuations.
Every body is investing in Wind Energy
• As crude oil prices escalate
3
Climate change does not respect borders.
• Rising temperature by burning fossil fuels would cause sea levels to rise,
displacing tens of millions of people .
Only Solution is renewable green energy specially “Wind Energy”.
• Total investments around $300 billion worldwide.
Economical, all weather, renewable, plentiful, widely distributed, clean, produces no
greenhouse gas emissions .
4. Why VAWT
Advantages:
• No yaw mechanism need for varying wind direction.
• Capable of operating during minimal wind speed.
• Does not have to installed at a very high place via tower.
Disadvantages:
• The lower the place, the slower the wind, reduces the turbines efficiency
4
Main Two type of turbine: Horizontal and Vertical axis
Advantages
• Research and development has reached stagnant stage .
• Has achieved its maximum efficiency limit.
• Disadvantages:
• Limited used for city conditions.
VAWT perfectly suited for city
conditions
5. Issues address in present work.
Very less reliable material available for VAWT.
• Very less experimental data available to validate CFD simulation.
• Even if experimental data is available, case setup data is not
available.
• Even if experimental data and case setup is available only COP is
compare . Detail flow physics is not explain.
• In many cases experiment is done on single Airfoil, thus the effect of
turbulence created by leading profile on the trailing is not captured .
• Performance is over predicted in CFD simulations.
A comprehensive and detail analysis is need
5
6. Objective
• The main objective of this project is to evaluated performance of high
solidity (VAWT) with multiple airfoils configuration using (CFD) software
for simulation.
• Secondly to develop a robust process to test numerous profiles with
minimum resources and time.
• Third is to give strong robust platform for future work through ‘Process
Oriented Approach’
Reliable, Consistent, Reproducible and Easy to use
6
7. License utilization :
• Open Source and unlimited licenses .
Machine utilization:
• Initial runs, test cases and utility development can be done on laptop .
• No need to reserve work stations.
• Total work from home environment.
Time utilization
• No waiting time for license availability on clusters for multiple case runs.
• No waiting time for Work Station availability.
Man Power utilization :
• Development of meshing utility reduced meshing time to few minuets.
• Setting of cases for is fatigueless.
• Easy to use and automated post-processing utility reduces human errors.
Why OpenFOAM
7
License , Machine , Time and Man Power
utilization were achieved
8. OpenFOAM using C++ Utility and its capabilities.
Mesh Generation process using C++ Utility (First 120° sector Profile Generation )
8
9. OpenFOAM using C++ Utility and its capabilities.
Mesh Generation process using C++ Utility ( Vertices Generation)
0
1
9
824
7
3
10 6
5
17
16
14
15
13
12
11
27
22
21
2019
18
43
44
25
24
23
26
46
47
45
42
32
31
30
29
28
41
34
33
40
39
38
37
36
35
Nodes
9
11. OpenFOAM using C++ Utility and its capabilities.
First 120° sector First and Second sector
First and Second and Third sectorFinal Mesh
11
12. OpenFOAM using C++ Utility and its capabilities(Domains).
Square Domain with Shaft Square Domain without Shaft
Circular Domain without ShaftCircular Domain with Shaft
12
13. OpenFOAM using C++ Utility and its capabilities(Domains).
c
c/2
a δ
R
β
Offset toward ‘le’
c
c/2
a δ
R
-β
Offset toward ‘tte’
c/2
a
R
β
No Offset toward
c
R
β
Offset with angle of attack Solidity (σ) > 0.4
Solidity (σ) < 0.4
13
14. OpenFOAM using C++ Utility and its capabilities(Domains).
In built symmetric NACA profile creation
Non-symmetric profiles form file with co-ordinates
14
15. Case Setup - Boundary conditions and Initialization
In built symmetric NACA profile creation
• Solver: kω-SST
15
16. Case Setup - Boundary conditions and Initialization
Common Parameters for High Solidity Configuration
Varying Parameters for High Solidity Configuration
Velocity is kept constant to keep Re = constant
Varying Angular velocity
16
17. Case Setup - Boundary conditions and Initialization
defined as the ratio between the tangential speed at
blade tip and the actual wind speed.
The rotor solidity, , basically describes what fraction of
the swept area .
As the rotor spins, the local azimuth angle for
each individual blade changes, and with it, so
does relative velocity (W) and angle of attack .
17
18. Reference Case for Validation.
• This Case setup is based on Ph.D. Thesis by Kevin W. McLaren McMaster
University (2011) .
• It’s a High solidity based work which is in line to the work done here our
group.
• This thesis was chosen because it has comprehensive and detail
experimental and numerical analysis of working vertical axis wind turbine.
• A great deal of literature on VAWT’s form McMaster university on similar
types of VAWT’s maintains the continuity of thought process.
• Good amount of experimental and CFD results helps in validation and
process building.
18
19. Mesh Validation.
• Reduction of y+ value increase value of ct..
• Reducing y+ is increase in peak amplitude in first half of revolution and reduction of second.
• Reducing y+ shifts the peak to right and broadens it in first half while shrinking and shifting it towards left in
other half.
Effect of Mesh count and y+ Configuration NACA15 and TPR 1.8 with (k = 1.5 and ω = 5.6)
19
22. • As shown in figure , negative torque this attributed to low pressure
region near leading edge on upper surface and near trailing edge on lower.
• This create a ’tow in’ or ’+’ condition
Result and Discussion – (Analysis)
.
0° to 30°
22
23. Result and Discussion – (Analysis)
.
45° to 90°
• Maximum torque is produces around 90°.
• NACAxx and S1046 profiles have almost same peak (ct) while DU-06-W200
produce has least (ct).
23
24. Result and Discussion – (Analysis)
.
• NACA0018 and DU-06-W200 that pressure drop but also a balanced low pressure regions
concentrated both at leading and trailing edges.
• Performance of S1046 not good because of concentrates the low pressure zone towards
the trailing edge creating a large negative moment reducing the torque (’tow-in’).
90° to 180° :
24
25. Result and Discussion – (Analysis)
• Turbulence produced by the preceding airfoils interfering with in succeeding one,
reducing the performance of the airfoil
• More pressure difference on S1046 increases the torque.
180° to 225° :
25
26. Conclusion
• Reliable, Consistent, Reproducible and Easy to use
• A comprehensive and detail analysis was done
• This observation is in the line of conclusion drawn by (Jacobs E. N, 1937) and
(Sidny F, 1980), which says that Increasing the thickness beyond 18% is usually
accompanied by a loss in efficiency
• Meshing and post-processing time is reduce drastically to few minutes by
developing OpenFOAM utility using C++ .
• Simulation time is reduce to 12 hours for one revolution using only 2 nodes
(24*2) processors on HPC clusters thus saving expensive computation time.
• NACA 0018 emerged as most efficient airfoil not only because of its shape and
thickness but taking into account turbulence interference of leading airfoil
26
