college of engineering aerodynamic effects of painted surface roughness on wind turbine blade...
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College of Engineering
Aerodynamic Effects of Painted Surface Roughness on Wind Turbine
Blade Performance
06/09/2015
Liselle A. JosephAurelien Borgoltz
Matthew Kuester
William Devenport
Julien Fenouil
Special thanks to Wind Turbine Aerodynamics Team of GE Power and Water
Joseph et al. NAWEA Symposium 2015
•Roughness is known to
decrease lift (Abbott and Von Doenhoff, 1959; Jones, 1936) Increase drag (Abbott and Von Doenhoff, 1959; Jones, 1936) Move transition forward (Timmer, 2004)
•Roughness on wind turbine blades (icing, soiling, coat deterioration etc.) reduces performance (Sagol, 2013; Ehrmann, 2014; Dalili et al., 2009)
•These are the main types of roughness currently under study
•No work into the effect of orange-peel type roughness
Likened to surface of an orange More wavy than peaky Produced from painting techniques and manufacturing processes
Importance of Roughness Effects
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Joseph et al. NAWEA Symposium 2015
•Created by painting Contact© paper with latex paint using rollers of various types
•Number of coats and painting direction were also varied
•3 configurations created and tested
(a) (b) (c)
Images of the Roughness Configurations (a) S1 (b) S2 and (c) S3. The scale of the roughness features is illustrated using the 12.5-mm grid superimposed on the S1 roughness
12.5mm
12.5mm
Roughness Fetches
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Joseph et al. NAWEA Symposium 2015
•Approximate values of roughness parameters measured using Mahr PS1
•In order of increasing roughness heights: baseline, S1, S2, S3
Baseline
(Unpainted Contact© Paper)
S1 S2 S3
1.6 4.0 6.1 10.7
13.5 28.6 38.7 62.9
2.9 10.1 17.7 23.4
Roughness Fetches
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Joseph et al. NAWEA Symposium 2015
Chord (m) Re (x106) Configuration Rek1
0.8
2
baseline 0.4
S1 4.4
S2 12.7
S3 21.3
3
baseline 0.7
S1 7.9
S2 22.5
S3 37.5
0.46
1.5baseline 0.7
S3 24.0
2baseline 1.1
S2 48.2
• Two DU96-W-180 models tested, each at 2 chord Reynolds Numbers
• Smooth and rough cases tested for each model
• Roughness Reynolds Number formulations:
• Below Rek1,crit effects are small, above Rek1,crit effects become more noticeable
Rek 1=𝑅𝑞𝑢k𝜈
Test Matrix
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Joseph et al. NAWEA Symposium 2015
•Experiments done in VT stability Wind Tunnel
•Lift and drag obtained from pressure measurements from test section wall and drag rake
•Transition obtained from infrared transition detection system
•Model wrapped in contact paper, 0.8-mm insulator, then roughness fetch
Experimental Set Up
0.8-mm silicone rubber insulator Starboard
mounted IR camera
Drag rake
Port mounted IR camera
Downstream View of 0.80-m DU96-W-180 Mounted in Wind Tunnel with Infrared Thermography System
Aluminum model with internally mounted heaters
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Joseph et al. NAWEA Symposium 2015
•Positive stall: αc~ 9°to10°
•Negative stall: αc~-14°
•Zero-lift αc~ -2°
•Baseline cases for two models of different chord lengths agree
Results
-20 -15 -10 -5 0 5 10 15 20-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
c
Clw
c
0.80-m DU96 Re=2.0M, baseline, Rek1=0.4
0.46-m DU96, Re=2.0M, baseline, Rek1=1.1
Variation of Lift and Drag for Different Chord Length Models, in Baseline Configuration, at Fixed Chord Reynolds Number of 2.0x106
-15 -10 -5 0 5 100
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
c
Cdw
c
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•Max lift and lift curve slope decrease with increasing Rek1
•effect most apparent at positive αc, especially above αc=5°
•Above Rek1 ~ 23 effect of roughness becomes much larger than below this value
•Rek1crit ~ 23
Effect of Roughness on Lift
Lift Plots for Varying for the DU96-W-180 (0.46-m and 0.80-m chords) at between 1.5x106 and 3.0x106
-15 -10 -5 0 5 10
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
c
Clw
c
c=0.80m, Rec=2.0.M, baseline, Re
k1=0.4
c=0.80m, Rec=3.0M, baseline, Re
k1=0.7
c=0.46m, Rec=1.5M, baseline, Re
k1=0.7
c=0.46m, Rec=2.0M, baseline, Re
k1=1.1
c=0.80m, Rec=3.0M, S1, Re
k1=7.9
c=0.80m, Rec=2.0M, S2, Re
k1=12.7
c=0.80m, Rec=2.0M, S3, Re
k1=21.3
c=0.80m, Rec=3.0M, S2, Re
k1=22.5
c=0.46m, Rec=1.5M, S3, Re
k1=24.0
c=0.80m, Rec=3.0M, S3, Re
k1=37.5
c=0.46m, Rec=2.0M, S2, Re
k1=48.2
6 8 10 12
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
c
Clw
c
6 8 10 12
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
1.05
1.1
1.15
c
Clw
c
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Joseph et al. NAWEA Symposium 2015
•Drag in bucket increases with increasing Rek1
•effect most dominant at positive αc
•Above Rek1 ~ 24 effect of roughness becomes much larger than below this value
•Rek1crit is between 20-25 (accounting for 10% uncertainty)
Effect of Roughness on Drag
-15 -10 -5 0 5 100
0.005
0.01
0.015
0.02
0.025
0.03
c
Cdw
c
c=0.80m, Re
c=2.0.M, Re
k1=0.4
c=0.80m, Rec=3.0M, Re
k1=0.7
c=0.46m, Rec=1.5M, Re
k1=0.7
c=0.46m, Rec=2.0M, Re
k1=1.1
c=0.80m, Rec=3.0M, Re
k1=7.9
c=0.80m, Rec=2.0M, Re
k1=12.7
c=0.80m, Rec=2.0M, Re
k1=21.3
c=0.80m, Rec=3.0M, Re
k1=22.5
c=0.46m, Rec=1.5M, Re
k1=24.0
c=0.80m, Rec=3.0M, Re
k1=37.5
c=0.46m, Rec=2.0M, Re
k1=48.2
Drag Plots for Varying for the DU96-W-180 (0.46-m and 0.80-m chords) at between 1.5x106 and
3.0x106
-15 -10 -5 0 5 100
0.005
0.01
0.015
0.02
0.025
0.03
c
Cdw
c
c=0.80m, Re
c=2.0.M, Re
k1=0.4
c=0.80m, Rec=3.0M, Re
k1=0.7
c=0.46m, Rec=1.5M, Re
k1=0.7
c=0.46m, Rec=2.0M, Re
k1=1.1
c=0.80m, Rec=3.0M, Re
k1=7.9
c=0.80m, Rec=2.0M, Re
k1=12.7
c=0.80m, Rec=2.0M, Re
k1=21.3
c=0.80m, Rec=3.0M, Re
k1=22.5
c=0.46m, Rec=1.5M, Re
k1=24.0
c=0.80m, Rec=3.0M, Re
k1=37.5
c=0.46m, Rec=2.0M, Re
k1=48.2
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Joseph et al. NAWEA Symposium 2015
•Below Rek1~23 L/Dmax slowly declines
•Large decrease in L/Dmax after Rek1~23
•Rek1crit ~ 20-25
Effect of Roughness on Lift-to-Drag Ratio
0 10 20 30 40 500
20
40
60
80
100
120
Rek1
L/D
max
datacurve fit
Variation of Maximum Lift-to-Drag Ratio with for the DU96-W-180 (0.46-m and 0.80-m chords) at between 1.5x106 and 3.0x106
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Joseph et al. NAWEA Symposium 2015
•Infrared transition detection system used to detect transition
•Gradient observed in images is onset of transition
•Image processing techniques used to extract %chord location AOA=0
IR Trans region ~56%(8.5" from TE)
AOA=0
IR Trans region ~61%(7.5" from TE)
Infrared Images of the Pressure Side of the 0.46-m DU96-W-180 at AoA=0° showing the Forward Movement of the Transition Front from the (a) Baseline case with Ra=1.58 to (b) S3 Roughness
case with Ra=6.78
FLOW
(a) (b)
Effect of Roughness on Transition
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Joseph et al. NAWEA Symposium 2015
-10 -5 0 5 100
10
20
30
40
50
60
70
80
, dg
x/c,
%
Rec=2.0M, Re
k1=0.4
Rec=3.0M, Re
k1=0.7
Rec=2.0M, Re
k1=4.4
Rec=3.0M, Re
k1=7.9
Rec=2.0M, Re
k1=12.7
Rec=2.0M, Re
k1=21.3
Rec=3.0M, Re
k1=22.5
Rec=3.0M, Re
k1=37.5
-8 -6 -4 -2 0 2 4 6 8 10 1210
20
30
40
50
60
70
80
90
100
, dg
x/c,
%
Rec=2.0M, Re
k1=0.4
Rec=3.0M, Rek1=0.7
Rec=2.0M, Rek1=4.4
Rec=3.0M, Rek1=7.9
Rec=2.0M, Rek1=12.7
Rec=2.0M, Rek1=21.3
Rec=3.0M, Rek1=22.5
Variation of transition location with angle of attack on the (a) Suction and (b) Pressure Side of the 0.8-m for all Rek1
Effect of Roughness on Transition
Suction Side Pressure Side
0.8-m DU96-W-180
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Joseph et al. NAWEA Symposium 2015
-10 -5 0 5 100
10
20
30
40
50
60
70
80
, dg
x/c,
%
Re
c=1.5M, Re
k1=0.7
Rec=1.5M, Rek1=24.0
Rec=2.0M, Re
k1=48.2
-10 -5 0 5 100
10
20
30
40
50
60
70
80
, dg
x/c,
%
Rec=1.5M, Re
k1=0.7
Rec=2.0M, Re
k1= 1.1
Rec=1.5M, Re
k1= 24.0
Rec=2.0M, Re
k1= 48.2
Variation of transition location with angle of attack on the (a) Suction and (b) Pressure Side of the 0.46-m for all Rek1
Effect of Roughness on TransitionSuction Side Pressure Side
0.46-m DU96-W-180
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Joseph et al. NAWEA Symposium 2015
Orange-peel type painted surface roughness on wind turbine blades have an effect on the performance
It was found that:
•Roughness effects show dependence on Rec and Rek
•The effect of the roughness is more pronounced at positive angles of attack
•Lift decreases gradually with increasing Rek, up to the critical Rek
•Drag increases gradually with increasing Rek, up to the critical Rek
•Transition moves forward slightly with increasing Rek, up to the critical Rek
•Critical Rek for orange-peel roughness is between 20 and 25.
Conclusions
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Joseph et al. NAWEA Symposium 2015
Effect of Roughness on T-S Waves
•Roughness induced disturbances grow and overtake natural T-S waves
•Roughness-induced T-S waves cause linear transition front upstream of natural transition
0 2 4 6 8 10 12 14 16 180
0.2
0.4
0.6
0.8
1
1.2
1.4x 10
-3
Wavelength, mm
Nor
mal
ize
d P
SD
S1S2S3
Averaged wavelength spectra of the painted roughness surfaces
0 5 10 15 20 25 30 35 400
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength, mm
Norm
alize
d I
nte
gra
ted
Gro
wth
0.46-m chord, Re = 1.5x106
0 5 10 15 20 25 30 35 400
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength, mm
Norm
alize
d I
nte
gra
ted
Gro
wth
0.46-m chord Re = 2.0x106
0 5 10 15 20 25 30 35 400
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength, mm
Norm
alize
d I
nte
gra
ted
Gro
wth
0.80-m chord, Re = 2.0x106
0 5 10 15 20 25 30 35 400
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Wavelength, mm
Norm
alize
d I
nte
gra
ted
Gro
wth
0.80-m chord, Re = 3.0x106
= -5 deg., Pressure Side: x/c=10% = 0 deg., Pressure Side: x/c=50% = 5 deg., Pressure Side: x/c=70% = -5 deg., Suction Side: x/c=55% = 0 deg., Suction Side: x/c=50% = 5 deg., Suction Side: x/c=40%
Wavelengths of unstable Tollmien-Schlichting disturbances for (a) 0.46-m DU96-W-180 at Re=1.5x106 and (b) 0.80-m DU96-W-180 at Re=1.5x106
(a)
(b)
Joseph et al. NAWEA Symposium 2015
Analysis of Effect on Performance
•XFOIL used to investigate whether changes in lift and drag are from changes in transition
•XFOIL ‘tripped’ at where transition is observed on IRT images for rough cases
•Differences compared to that observed between clean and rough results
-10 -5 0 5 10-1
-0.5
0
0.5
1
1.5
, deg.
Cl
-10 -5 0 5 100.006
0.008
0.01
0.012
0.014
0.016
0.018
0.02
, deg.
Cd
-10 -5 0 5 10-0.5
0
0.5
1
1.5
2
2.5
3
3.5x 10
-3
, deg.
C
d
-10 -5 0 5 10-0.07
-0.06
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
, deg.
C
l
Clean - ExperimentS3 - ExperimentClean - XFOILS3 - XFOIL
Cl - Experiment
Cl - XFOIL
Cd - Experiment
Cd - XFOIL
XFOIL analysis of the effect of transition location on lift and drag. XFOIL transition locations were set from IR transition measurements for the 0.46-m DU96-W-180 Model at Re = 1.5x106. Differences in (a)
lift and (b) drag are between the clean model (covered in insulator) and the S3 roughness condition.
(a) (b)