Post on 23-Aug-2020
transcript
18 March, Vienna Xia ojia n Hua ng, Cra nfie ld University, UK
Simula tion of VAW T for wa ke e ffects
Scope
• What we do? • Why we do? • What is available? • How we do? • What we learn? • What to do next?
W hat we do?
• Cranfield University • Energy and Power Engineering Division • Renewable Energy
• Wind, Wave & Tidal, Biomass, CCS • Wind
• VAWT(NOVA) • Offshore supporting structure(H2OCEAN) • Power system • Reliability models
W hy we do?
• Wake effects are important, many questions can be asked for VAWT
• Dynamic stall • Complex flow structure • Limited measurement
• Simulation
W hat is available?
• Desktop Computer • Core i5 4G RAM (Windows based)
• High Performance Computer(HPC) at Cranfield • Astral/Grid (Linux based)
• STAR-CCM+ v7.06.009 up to 32 processors • Measurements from NASA and Sandia National
Laboratory (SNL)
Two major tasks before solution
• Get the mesh setting right • How big can the model be?! For the 4G RAM
• 0.5G RAM per million cells for trimmer mesher • 2G RAM per million cells for polyhedral mesher
• Get the physics setting right • URANS + Turbulence models • General RAM requirement for solution
• 0.5G RAM per million cells for segregated solver • 1G RAM per million cells for explicit coupled solver • 2G RAM per million cells for implicit coupled solver
How we do?
• Start with simple cases! • Dynamic stall of airfoil
• Morphing(Deformed mesh) • VAWT simulation
• Rigid Body Motion
Oscillating a irfoil?
• 3 different regimes from NASA experiment • No stall : AOA=4+4sinωt; ω=2.199 • Light stall : AOA=11+4sinωt; ω=5.445 • Deep stall: AOA=17+5sinωt; ω=5.445 • Velocity 29m/s
Model setup
• No stall • Light stall • Deep stall
• Motion: morphing/rotation
No stall video (AOA=4°+4°sinωt)
Light sta ll video (AOA=11°+4°sinωt)
Deep sta ll video (AOA=17°+5°sinωt)
Oscillating a irfoil No sta ll ca se
0
0.1
0.2
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0 1 2 3 4 5 6 7 8 9
CL
Alpha(°)
No stall case-Alpha=4+4sin(2.199t)
NASA
K-O
Light stall case
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
6 8 10 12 14 16
CL
Alpha(°)
Light stall case-Alpha=11+4sin(5.445t)
NASA
k-epsilon
S-A
K-O
Deep stall case
-0.5
0
0.5
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1.5
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2.5
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10 15 20 25
CL
Alpha(°)
Deep stall case-Alpha=17+5sin(5.445t)
NASA
K-epsilon
S-A
K-O
Rotating turbine
• Sandia-17m VAWT • Rotor Diameter=16.7m • Rated Power=100kw • Rotor speed=38.7 rpm • TSR=2.33 and TSR=4.60 • NACA0015
Local AOA (Low wind speed)
Local AOA (High wind speed)
Model setup
• Cell Number Count=~580000
• Viscous flow solved by implicit unsteady solver
• S-A turbulence model • Time step=0.0043s(to
ensure 360 time steps per revolution)
Simulation video(7.35m/s)
Simulation video(15.6m/s)
TSR=4.60 (Low wind speed)
-1.5
-1
-0.5
0
0.5
1
1.5
-90 -30 30 90 150 210 270
Nor
mal
forc
e co
effic
ient
Azimuth angle
Normal force coefficients(TSR=4.60)
Experimentaldata
STARCCM+2
TSR=2.33 (High wind speed)
-2
-1.5
-1
-0.5
0
0.5
1
1.5
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-90 -30 30 90 150 210 270
Nor
mal
forc
e co
effic
ient
Azimuth angle
Normal force coefficients(TSR=2.33)
Experimental data
StarCCM+
TSR=2.33 (High wind speed)
-0.2
-0.1
0
0.1
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0.3
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-90 -30 30 90 150 210 270
Tang
entia
l for
ce c
oeffi
cien
t
Azimuth angle
Tangential force coefficients(TSR=2.33)
Experimental data
StarCCM+
W hat we learn?
• Simulation using STAR-CCM+ has given fair to good lift predictions for oscillating airfoil
• None of the turbulence models could account for all the regimes, S-A model gives better prediction in the deep stall case tested.
• Near wake simulation of rotating VAWT is validated under two different wind regimes, force predictions show acceptable agreement with the experimental data using S-A turbulence model.
W hat to do next?
• Mesh settings • Solver settings • Turbulence models • Far wake predictions • Co-simulation
Acknowledgement
• To Professor Feargal Brennan for his supervision and support
• To Andy Gittings for assistance in simulation on the HPC cluster
• To Michael Descamps from CD-adapco who kindly shared knowledge regarding morphing with me through email
Reference
• CD-adapco (2012) STAR-CCM+ User Guide 7.06 • Rhee, M. J. (2002). A study of dynamic stall vortex
development using two-dimensional data from the AFDD oscillating wing experiment (No. AFDD/TR-02-A-009). ARMY AVIATION RESEARCH AND TECHNOLOGY ACTIVITY MOFFETT FIELD CA AEROFLIGHTDYNAMICS DIRECTORATE.
• Paraschivoiu, I. (2002). Wind turbine design: with emphasis on Darrieus concept. Presses inter Polytechnique.
• Allet, A., & Paraschivoiu, I. (1995). Viscous flow and dynamic stall effects on vertical-axis wind turbines. International Journal of Rotating Machinery, 2(1), 1-14.
Thank you! Questions?