EXPERIMENTAL CHARACTERISTICS OF WIND TURBINE
BLADING OVER FULL 0 TO 360 DEGREE
ANGLE OF ATTACK
April 2014
Project Number : RD-RD-400-11
Dr. A.P. Haran
Prof. Soundranayagam
Prof.J.J. Isaac
Professor, H.O.D
Professor
Professor
Department of Aeronautical Engineering
Park College of Engineering and Technology
Anna University
Kaniyur, Coimbatore -641659
NOTICE
This report was prepared as an account of the work sponsored by
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their employees, makes any warranty, express or implied, or assumes
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No part of this report shall be either reproduced or otherwise be
used in any form without the written permission of the C-WET and the
proponent.
Available electronically at http://www.cwet.res.in
EXPERIMENTAL CHARACTERISTICS OF WIND TURBINE
BLADING OVER FULL 0 TO 360 DEGREE
ANGLE OF ATTACK
April 2014
Project Number : RD-RD-400-11
Dr. A.P. Haran
Prof. Soundranayagam
Prof.J.J. Isaac
Professor, H.O.D
Professor
Professor
Department of Aeronautical Engineering
Park College of Engineering and Technology
Anna University
Kaniyur, Coimbatore -641659
ACKNOWLEDGEMENTS
The Centre for Wind Energy Technology (C-WET) would like to
acknowledge the experts from Park College of Engineering and
Technology, Anna University, Kaniyur, Coimbatore – 641 659, who have
authored this report.
C-WET also thanks the Ministry of New and
Renewable Energy (MNRE) for their financial and technical support for
the research and production of this report.
Major contributors in alphabetical order include :
Dr. A.P. Haran
Prof. Soundranayagam
Prof.J.J. Isaac
Professor, H.O.D
Professor
Professor
CHAPTER NO.
1.
TITLE
INTRODUCTION
PAGE NO.
1
2.
EXPERIMENTAL SETUP AND CALIBRATION
1
3.
EXPERIMENTAL VALIDATION
3
4.
AEROFOILS PERFORMANCE CHARACTERISTICS
5
4.1
BLADE LOCATION IN THE TEST SECTION
5
4.2
CONFINED FLOW ANALYSES
[CLOSED TEST SECTION]
4.3
5
ANALYSIS WITHOUT CONFINEMENT:
[HALF OPEN TEST SECTION]
7
4.3.1 NWT 1001
7
4.4
NWT 2004
9
4.5
NWT 2005
11
5.1
LIFT AND DRAG AT DEEP-STALL ANGLES
12
6.1
CONCLUSION
13
7.1
REFERENCES
15
APPENDIX -I
C P PLOT FOR VARIABLE ANGLES ATTACK
WITHOUT CONFINED FLOW NWT 1001
16
2
C P PLOT FOR VARIABLE ANGLES OF ATTACK [NWT 2004]
30
3
C P PLOT FOR VARIABLE ANGLES OF ATTACK [NWT 2005]
40
1
NOMENCALURE
p
Static pressure on the aerofoil surface
p∞
Reference pressure
ρ
Density of air
V∞
Free stream velocity
α
Angle of attack
R
Resaultent force
L
Lift
D
Drag
N
Normal force
A
Chord wise force
Cp
Local pressure co efficient
Cl
Co efficient of lift
Cd
Co efficient of drag
Cn
Co efficient of normal force
Ca
Co efficient of chord wise force
Re
Reynolds number
1. Introduction
Most of the wind turbines in our country are based on imported technology and design. It is
often felt that their performance characteristics are not well suited to the Indian wind regime.
Since India is one amongst the world leaders in harvesting wind power, it is important that the
wind turbine used in India should be suitable to the Indian wind condition and be based on
indigenous technology. Hence, the information would be of special importance in the design of
stall regulated wind machines. Special attention should be paid to the flow regime immediately
around the stall point and at high angles of attack. This knowledge is essential for the
understanding of its starting capability and low speed performance. But in India the resources
about the high angle of aerodynamics is limited, hence this experimental study would be of great
importance to wind turbine designers.
Blade profiles designed for a particular capacity of wind turbine by National Aerospace
Laboratories viz, as NWT1001, NWT2004, NWT2005 Tip section, mid span and Root section of
the blade respectively were obtained and used for the experiment and CFD simulation. the blade
profiles are showing in figure 1(a). The above blading belonged to the stall regulated class of
wind turbine. An indigenous wind turbine blading has been evaluated for angles of attack
ranging from 0o to 360o using low speed wind tunnel. The wind turbine performance can
normally be predicted through the use of the blade element momentum theory together with two
dimensional aerodynamic data. This method has been used to obtain lift and drag characteristics
of the blade from the data obtained from the wind tunnel testing. The wind turbine blades are
tested at give a Reynolds number around 200,000 which is far above the critical Reynolds
number of similar airfoils for angles of attack varying from 0o to 360o.
NWT1001
NWT2004
NWT1001
0.2
NWT2004
NWT2005
0.1
0
-0.1
0
NWT1001
0.2
Figure 1(a): Wind turbine profiles
1
0.4
0.6
All Profiles
0.8
1
2. Experimental set up and calibration
The experiments were performed in a blower type low speed wind tunnel. The centre line
height is 48 inches (1200 mm) which is very convenient for most experimental purposes. A
centrifugal blower draws air from the room and delivers it horizontally into a long straight
diffuser. A vertical central splitter approximately one of the diffuser lengths is installed at
diffuser inlet. The flow from the diffuser enters a 6feet x 6feet (1830mm x 1830mm) plenum
chamber where it passes through a honeycomb and a set of wire screens before entering the test
section to provide uniform flow with low turbulent intensity. The general purpose test section
has Perspex side walls and plywood roof and floor. The flow leaving the test section is left free
to the outside atmosphere. A large filter box lined with fine muslin, about 2000 mm cube can be
fitted to enclose the blower inlet to minimize dust interference with hot wire probes. The
general purpose test section is 24inches (610 mm) square and 5feet (1525 mm) long.
The tunnel calibration was done to capture the wall boundary layer thickness which was
found to be 15 mm from each wall of the tunnel. The turbulence intensity in the test section was
measured using Hot Wire Anemometer and found to be 0.7% at maximum velocity of wind
tunnel.
The pressure distribution over the blade was measured using 32-channel SCANIVALVE
pressure sensors. The model is placed along the centreline of the test section with the help of the
mounting arrangement. An indexing disc which permits rotation of the blade through 360o in one
degree step, is placed and tightened on top of the model over the test section of the tunnel. The
photo of the indexing mechanism is shown in figure 1(b).
Figure 1(b): Indexing arrangement.
2
3. Experimental validation
Figure 2. Forces acting on the aerofoil
Figure 2. shows forces acting over an aerofoil. Based on the pressure measurements on
the suction side and pressure side, pressure coefficient is calculated using the formula given
below and plotted against x/c i.e. along the chord for different angles of attack. The cp
distributions obtained for various angles of attack are shown in figure 3(a). The airfoil
characteristics obtained from the experiments for angles of attack up to 16 degree are compared
with CFD results. As the results are comparable, experiments were conducted for the rest of the
angle of attack up to 360 degree.
Cp =
2 ( p − p∞ )
ρV∞ 2
Figure 3(b) shows the plot of pressure co efficient against chord wise direction for the
angle of attack of 8 o. There is a good match between the experiment and the CFD results. The
flow separation noticed at 18 % of the chord in the suction surface of the blade has been
predicted by CFD and is shown in Figure 3(c).
Lift and drag co efficient were estimated using the following formulae. Cn and ca are
calculated by integrating the pressure coefficient along the chord and the normal to the chord
respectively.
=
Cl Cn cos α − Ca sin α
=
Cd Cn sin α + Ca cos α
Figures 4 and 5 show the variation of lift and drag co efficient with α. Estimated values of lift
and drag co efficient obtained from the experiments for angles of attack up to 12 degree, the
angle of attack prior to stalling, agree well with the CFD predictions. Beyond stall lift and drag
do not match with CFD results because the flow becomes largely separated. The turbulence is
modelled and validated using the results obtained from the attached flow and mildly separated
flow experiments. Hence these models are very poor in predicting highly separated flows for
angles of attack beyond stall.
3
presure side
1.00
Angle of attack =0o
suction side
0.50
0.50
0.00
0.00
-1.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
presure side
50
X/C
60
70
80
90
100
-3.00
0
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
10
20
30
40
presure side
50
60
X/C
70
suction side
80
90
20
30
40
presure side
1.00
0
10
Angle of attack = 8o
suction side
1.00
Cp
Cp
Angle of attack = 4o
suction side
-0.50
-1.00
Cp
Cp
-0.50
50
X/C
60
70
80
90
100
Angle of attack = 10o
suction side
-3.00
100
0
10
Angle of attack = 16o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
presure side
1.00
20
30
40
presure side
50
X/C
60
70
80
90
100
Angle of attack = 20o
suction side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
X/C
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
Figure 3(a): Pressure Distribution over the aerofoil for angles of attack from 0 to 20 degree
4
90
100
1.00
Angle of attack = 8o
0.50
0.00
Cp
-0.50
-1.00
-1.50
pressure side p(1 & 3)
suction side P(1 & 3)
CFD
-2.00
-2.50
-3.00
0
20
40
X/C
60
80
100
Figure 3(b): Pressure distribution over the airfoil
Figure 3(c): Computed streamlines on NWT 1001
1.4
0.4
1.2
0.35
0.3
1
0.25
Cd
Cl
0.8
0.6
0.2
0.15
0.4
Computational
5
10
15
20
Computational
0.05
0
0
Experimental
0.1
Experimental
0.2
0
25
0
Alpha
Figure 4: Co efficient of lift vs. Alpha
5
10
Alpha
15
20
25
Figure 5: Co efficient of drag vs. Alpha
4. Aerofoils Performance Characteristics:
4.1. Blade Location in the Test Section:
The detailed experimentation was done for all the blades in the open i.e. the blades were
kept two chord downstream of the exit of the test section. In this position, the flow field will face
minimum confinement and hence mimics the actual flow condition.
To differentiate between the performance of the blade in the free flow field and confined
flow field, NWT1001 blade was tested by mounting the blade inside the test section, wherein the
walls of the test section confine the flow around the blade. Under confined conditions, the
blockage to the flow increases with increasing angles of attack, reaching a maximum of 25
percentage at 90 degree and as per Rainbird [2] observations in the wind tunnel, measured 𝐶𝐿 𝑚𝑎𝑥
and 𝐶𝐷 𝑚𝑎𝑥 are higher by 20%
4.2. Confined Flow Analysis [Closed test section]:
Performance of the blade (NWT 1001) in term of Cl and Cd is evaluated by measuring the
blade pressure distribution for different angles of attack. The cp distributions are shown in
appendix - I. The blade pressure distribution is obtained by chord wise distributed pressure taps
5
of 0.8 mm diameter over the suction and pressure faces. Lift and drag co-efficients NWT1001
were estimated for angles of attack varying from 0o to 360o presented in figure 6, at Reynolds
number 200 000. As expected, it can be seen that the lift curve linearly increases and the
maximum co efficient occurs at 12o angle of attack. There-after it falls and then rises up to
44o.The cause of decrease in lift coefficient is due to unsteadiness over the aerofoil due to
separation at the trailing edge of the section side. Due to the constrained flow field, the airflow
on the suction side reattaches causing an increase in the lift coefficient up to 440 angle of attack.
With the increase in incidence beyond 440 , the flow is fully separated over the entire aerofoil
suction surface causing the lift co-efficient to fall rapidly to a negative value of 0.9 at an alpha of
140 degree from zero at 92 degree angle of attack. This position corresponds to a flat plate
facing the flow at right angles to the surface. With incidence further increasing lift co efficient
rises steadily from -0.9 to zero at an angle of attack of 180o.
Now, the trailing edge of the blade is facing upstream flow and it is creating the pressure
difference over an aerofoil which causes the lift co efficient rise to a value of 0.55 at an angle of
attack of 188o. Any further increase in the angle of attack causes a reproduction of the C L curve
but the maximum value of lift co efficient in this segment reaching 0.8 as against to 1.3 where
leading edge is facing the flow.
Co efficient of lift
Co efficient of drag
Estimated Cl
Estimated Cd
2.5
2
Cl Cd
1.5
1
0.5
0
-0.5
-1
-1.5
-30
-15
0
15
30
45
60
75
90
105
120
135
150
165
180
195
210
225
240
255
270
285
300
315
330
345
360
Alpha
Figure 6: Closed test section Cl and Cd(NWT 1001) blade.
The drag co efficient plot with alpha is close to a sinusoidal curve, the lower value at the
trough occurring at zero degree angle of attack (C d = 0.02), 180o and 360o angle of attack and
the peak values occurring at 82o (C d = 2.08) and at 272oangle of attack. At these angles of attack
the aerofoil acts like a bluff body (flat plate) causing complete breakdown of the flow and
creates a large re-circulating zones behind the airfoil.
The Lift and Drag co efficient curves plotted from the experimentally derived values and
estimated from the following formulae match very well indicating the accuracy of the
6
experimental results. The estimated values are derived from the flat plate theory. The results are
matching only at high angles of attack because at lower angles of attack the blade is behaving
like aerofoils but at high angles of attack this profile is behaving like a flat plate.
Cl = sin 2α
Cd = 2sin 2 α
The important observation in the lift curve is that the post stall C L value (C L =1.25) is
greater than the first-stall peak value of 1.0. This kind of phenomena never occurs in the real
flow field over an aerofoil. And hence, it is attributed to the effect of confined flow over the
blade.
4.3Analysis without Confinement: [Half open test section]
4.3.1 NWT 1001
As per the recommendations of Rainbird[3] to avoid wall effects at high incidences the
blade was kept outside of the wind tunnel, one and half feet away from wind tunnel test section,
that is to say half open test section was used. Figure7 shows the variation of estimated lift and
drag co-efficient with angles of attack. This continuous increase of lift coefficient with angle of
attack matches very well with the variation of lift coefficient in the confined flow up to pre-stall
(first peak). In the post stall regime, the lift coefficient slightly differs from the closed wall
analysis with the second peak reaching 0.97 as against 1.22 in the closed flow tunnel. There-after
there is no significant difference in the free flow analysis. Eventually with higher angles of
attack, the fully separated flow over suction surface of the aerofoil leading to a decrease in lift
coefficient followed by a sudden drop occurring at 68o through 72o,i.e 𝐶𝐿 value dropping to 0.31
from 0.59. This is an indication of the starting point of the separation bubble suddenly moving
towards the leading edge causing total flow separation on the suction surface. There-after the
drop in lift coefficient is gradual up to 1120. At 1120 the drop is sudden once again. The 𝐶𝐿 value
drops from -0.15 to -0.42.
As expected, in the post-stall regime, the flow is completely separated on the suction
surface of the aerofoil. It can be seen in figure 8. Almost the pressure coefficient is constant on
the suction side but the values differ with increasing angles of attack. There is a sudden variation
in the suction side pressure coefficient, with increasing angles of attack, which in turn leads to
changes in lift and drag coefficients. At 68o angle of attack, the flow on the suction side turns
over the leading edge before the onset of separation. At 72o angle of attack, the flow deviates
away from the suction surface creating a larger wake region. The drag coefficient curve, as
expected, starts off as a sine curve from 00 angle of attack but deviates from the curve with a
sudden drop at 68o through 72o. Again it follows the sine curve till 1120 where it shoots up
through 116o and then follows the sine curve. This phenomenon is well known and is called the
drag bucket.
7
AOA increasing Cl
AOA increasing Cd
AOA decreasing Cl
AOA decreasing Cd
AOA decreasing Cl
AOA decreasing Cd
Estimated Cl
Estimated Cd
2.5
2.0
1.5
Cl Cd
1.0
0.5
0.0
-0.5
-1.0
-1.5
-30
-15
0
15
30
45
60
75
90
105
120
135
150 165
Alpha
180
195
210
225
240
255
270
285
300
315
330
345
360
Figure 7: Open test section Cl and Cd Aerodynamics data (NWT 1001)
AOA 68 presure side
AOA 72 presure side
1.00
AOA 68 suction side
AOA 72 suction side
AOA 120 presure side
AOA 116 presure side
1.00
0.50
0.00
0.00
Cp
Cp
0.50
AOA 120 suction side
AOA 116 suction side
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
0
20
40 X/C
60
80
100
0
20
40
X/C
60
80
100
Figure 8: Pressure distribution over the aerofoil NWT 1001 for open section.
The sudden changes in lift and drag coefficient can be explained with the help of pressure
distribution and hence 𝐶𝑃 over the chord length. The change in the pressure distribution over the
pressure surface is marginal, where as it is flat and marked over the suction surface. The change
in area of the curve over the angle of attack is large enough to give a large change in lift and
drag coefficient. Similar trend follows for all angles of attack above 180o.
Another important feature to observe is the hysteresis loop in the 𝐶𝐿 and
𝐶𝐷 characteristics. While repeating the test by lowering the angle of attack from 180o to 0o, 𝐶𝐷
rose up to 112o followed by a sudden drop at 112o through 102o. Thereafter the trend continues
up to 60o at which it rises suddenly from 56o through 520 before following the sine curve.
Similar trend is captured in the 𝐶𝐿 curve.
Surprisingly the hysteresis loop occurs in the deep stall region instead of in the stall
region, as reported in the literature [4]. Due to the existence of multiple values of𝐶𝐿 and 𝐶𝐷 for a
given angle of attack in the hysteresis loop, the airflow over the blade will be unsteady causing
8
violent oscillations and hence fatigue. These regions should be taken care during the design and
if not possible to avoid during the design, the operation in this region is to be avoided totally. If
these blades are meant for vertical axis machines, the blades will be exposed to the hysteresis
loop during every rotation and hence such a design is not recommended for vertical axis
machines.
4.4. NWT 2004
The NWT 2004 aerofoil exhibits, as shown in figure 9(a), both a higher lift peak and
slightly more progressive and delayed stall compared with NWT 1001. In this case, stall occurs
at 20oangle of attack with a 𝐶𝐿 value of 1.58.Beyond stall 𝐶𝐿 drops up to 28o angle of attack and
then rises to reach a peak value of 1.27 at 32o.Thereafter it follows a similar trend and it closely
resembles the 𝐶𝐿 curve of NWT 1001.
AOA increasing cd
AOA Increasing Cl
AOA Decreasing Cl
AOA Decreasing Cd
Estimated Cl
Estimated Cd
2.5
2
1.5
Cl Cd
1
0.5
0
-0.5
-1
-1.5
-30
-15
0
15
30
45
60
75
90
105
120
135
150
165
180
195
210
225
240
255
270
285
300
315
330
345
360
Alpha
Figure 9(a): Open test section 𝐶𝐿 and 𝐶𝐷 Aerodynamics data (NWT 2004).
At 52o incidence, the separation bubble bursts causing separated flow occupying the complete
suction surface. Similar drop occurs at an angle of 1040 incidence. This flow behaviour is
analogous to NWT 1001. While conducting the tests with decreasing incidence the hysteresis
loop appears in both the 𝐶𝑙 and 𝐶𝑑 curves. The third and fourth loops observed in the
NWT 1001 beyond 1800 are not seen in this aerofoil (NWT2004).
Figure 9(b): Flow over an aerofoil NWT2004 at 90o
Figure 9(c): Flow over an aerofoil NWT2004 at 270o
9
The above phenomena can be explained using Figure 9 (a) and (b). The pressure /flat is facing
the flow when the angle of attack is around 90o. As a result the flow around the aerofoil is
similar to a wake behind a flat plate, whereas at around 270o the suction/curved surface of the
aerofoil meets the flow, thereby giving time for the flow to negotiate over the curved surface.
This creates a comparatively small wake region with less curvature due to this reason; the flow is
not separated completely and rather closer to the surface in the downstream of the aerofoil.
Figure 10 shows the pressure distributions over the aerofoil at various angles of attack.
At 0 the separation bubble is found on both the sides of the aerofoil. The location of the
separation bubble on the pressure side is from x/c 0.15 to 0.43 and from x/c 0.67 to 0.82 on the
suction side. The separation bubble on suction side is not seen at 4o angle of attack. Even though
the bubble is present on pressure side, the separation point is moved towards the trailing edge of
the aerofoil. The size of separation bubble is shrunk and lies between x/c 0.45 to 0.54. For
further increase in angle of attack the bubble gets smaller and completely suppressed at 12o angle
of attack.
o
presure side
1.00
Angle of attack = 0o
separation bubble
-0.50
-0.50
Cp
0.00
-1.00
-1.00
-1.50
-1.50
0
20
40
presure side
X/C
-2.00
60
suction side
80
100
0
Angle of attack = 8o
40
X/C
60
80
100
Angle of attack = 12o
suction side
1.00
separation bubble
0.50
0.00
0.00
-0.50
Cp
Cp
20
presure side
1.00
0.50
Angle of attack = 4o
suction side
0.50
0.00
-2.00
presure side
1.00
separation bubble
0.50
Cp
suction side
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
0
20
40 X/C
60
80
0
100
20
40
X/C
Figure 10: Pressure distribution over the Aerofoil for NWT 2004.
10
60
80
100
4.5. NWT 2005
The lift and drag characteristics of the NWT2005 aerofoil are shown in figure 11 and it can be
seen that, it closely resembles that of NWT2004 lift and drag curves. With increasing angles of
attack lift coefficient increases linearly reaching a peak value of 2.05after which it drops. The
stall is delayed as compared to the other two aerofoils. NWT2005 aerofoil is highly cambered as
compared to other two profiles. Hence, the profile is able to turn the flow even at higher angles
of attack.
Beyond stall, the flow is separated on both the suction and pressure surface as can be
seen in the pressure distribution in figure 12. The pressure distribution shown in fig 12 indicates
separation bubbles near the trailing edge on the pressure surface and at 20% of the chord on the
suction surface at 0o angle of attack. At 8o incidence the separation is seen in the leading edge on
the pressure surface. At 280 the separation bubble is seen on the trailing edge of the suction
surface and most part of the pressure surface. At 320 the flow remains attached up to 40% of the
chord on the suction surface and 20% of the chord on the pressure surface. With increase in
angle of attack from 00 to 280 the area within the pressure distribution keeps increasing with a
corresponding increase in 𝐶𝐿 .
Although, at some high angles of attack there are discontinuities in lift and drag coefficients, and this kind of phenomena has already been discussed with reference NWT2004. In
this case, this discontinuity lies between 72o to 120o angles of attack. The Cl and Cd curves
obtained while decreasing the angle of attack join the parent Cl and Cd curves over a large range
angle of attack as compared to NWT2004 where the Cl and Cd curves join parent curves sharply
AOA increasing cd
AOA Increasing Cl
AOA decreasing cl
AOA Decreasing cd
Estimated Cl
Estimated Cd
2.5
2
1.5
Cl Cd
1
0.5
0
-0.5
-1
-1.5
-30
-15
0
15
30
45
60
75
90
105
120
135
150
165
180
195
210
225
240
255
Alpha
Figure 11: Open test section C l and C d (NWT 2005) blade.
11
270
285
300
315
330
345
360
1.00
presure side
suction side
1.00
Angle of attack =0 o
0.50
suction side
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
0
20
40
X/C
60
80
0
100
20
40
60
100
(b)
suction side
Angle of attack
1.00
=8o
presure side
1.00
suction side
Angle of attack =12o
0.50
0.50
0.00
0.00
-0.50
Cp
Cp
80
X/C
(a)
presure side
-1.00
-0.50
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
0
20
40
X/C
60
80
0
100
20
40
presure side
1.00
60
X/C
(e)
80
100
(f)
suction side
Angle of attack
=28o
presure side
1.00
suction side
Angle of attack =32o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
Cp
Cp
Angle of attack =4 o
Cp
Cp
presure side
0.50
-1.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
-3.50
0
-3.50
0
20
40 X/C
60
80
100
20
40
60
80
100
X/C
(g)
(h)
Figure 12: Pressure distribution over the Aerofoil NWT 2005
Corresponding to figure 12, it becomes obvious that the separation bubble formed on the
pressure side shrinks and moves backwards towards the trailing edge while separation bubbles
on the suction side also shrinks in size but it instead moves forward towards the leading edge.
These comments seem to be valid for low angles of attack. For higher angle of attack separation
bubble bursts leading to stall.
5.1 Lift and Drag at deep-stall angles
The lift and drag force is based on pressure distribution over an aerofoil with increasing
and decreasing angles of attack. The ratio of Cl and Cd is plotted in figure 13 for all angles of
attack for all the three aerofoils. For lower angles of attack the Cl over Cd variation is like any
other aerofoils. For higher angles of attack around the deep stall region the slope of the Cl over
Cd curve is close to 0.025, coinciding with the estimated values using the formulae. This value is
same as the one given in reference [6]. At lower angles of attack and also at angles of attack
when the trailing edge facing the flow Cl over Cd curves are distinct and different from Cl over
Cd curve for the estimated values.
12
nwt 2004
NWT 2005
Estimated
NWT 1001
20.0
0.0
16.0
-4.0
12.0
-8.0
CL /Cd
Cl/Cd
NWT 1001
8.0
4.0
NWT 2004
Estimated
-12.0
-16.0
0.0
-20.0
0
10
20
30
40
50
Alpha
60
70
80
90
100
90
100
110
120
(a)
NWT 1001
NWT 2004
130
Alpha
140
150
160
170
180
(b)
NWT 2005
Estimated
NWT 1001
20.0
0.0
16.0
-4.0
12.0
-8.0
NWT 2004
Cl/Cd
Cl Cd
NWT 2005
8.0
-12.0
4.0
-16.0
0.0
180
190
200
210
220
230
240
250
260
270
-20.0
270
280
290
Alpha
(c)
Figure 13: Ratio of Lift and drag co efficient
300
310
Alpha
320
330
340
350
360
(d)
6.1 Conclusion:
All the three blades have been experimentally investigated over to 00 to 3600 for
Reynolds number 2 x 105.The blades exhibit two stall regions (hard and soft stall ) over 00 to
180O and again two stall regions over 1800 to 3600 deg, the Cl and Cd values in the second
region are smaller compared to the first. Stalling angles are 120, 200, 280 for the tip, mid and root
profiles respectively. While starting of the wind turbine angles of attack varies from 300 to 400
degree in the root to 600 to 800 in the tip regions. Since the Cl values for all the three blades are
about 0.6 around these angles of attack, the starting characteristics for the set of blades is good.
When operating at the design point, ratio of lift and drag values are kept high giving the design
power extraction from the wind turbine. Stall hysteresis for all the three blades are located at
deep stall regions and hence will not affect the starting and design point performance of the wind
turbine. These blades are not suitable for VAWT machines since they exhibit stall hysteresis.
Commercial CFD codes with proper attention to Reynolds number range and mildly
separated flows can be used to predict the performance of airfoils up to the stall regime. This can
be extended up to the complex three dimensional flows in an actual wind turbine unless the flow
13
detachment is not too large. For large angle of attack computations CFD is not a good tool to be
relied upon. Instead we can opt for numerical curve fit methods which are available in literature
for angles of attack after stall regime. With the use of these two tools combined together one can
design a better wind turbine with a good starting and operating characteristics.
14
7.1 References:
1. Wilson, R. and Lissaman, P. Applied aerodynamics of wind power machines, 1974
(State University, Oregon).
2. Wilson, R. Lissaman, P., and Walker, S. Aerodynamic performance of wind turbines,
1976 (State University, Oregon).
3. McCartyt, J. PROP93 Users guide, (Alternative Energy Institute).
4. Worasinchai, S. Ingram, G and Dominy, R. A low Reynolds-member, High-angle- of
attack investigation of wind turbine aerofoils, 2011(Durham University, UK).
5. Daniel J. Walter Study of Aerofoils at High Angle of Attack, in Ground Effect, school of
aerospace, mechanical & manufacturing engineering Portfolio of science, engineering &
technology Rmit university September 2007
6. W.A. Timmer , Aerodynamic characteristics of wind turbine blade airfoils at high
angles-of-attack, Delft University of Technology Faculty of Aerospace Engineering
Kluyverweg 1, 2629 HS Delft, The Netherlands.
15
Appendix I
1. Cp plot for variable angles attack without Confined flow NWT 1001
presure side
1.00
Angle of attack =0o
suction side
0.50
Angle of attack = 4o
suction side
0.50
0.00
0.00
-0.50
-0.50
-1.00
Cp
Cp
presure side
1.00
-1.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
60
70
80
90
100
-3.00
0
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
20
30
40
70
suction side
80
90
40
50
X/C
60
70
80
90
100
Angle of attack = 10o
suction side
-3.00
100
0
10
20
Angle of attack = 16o
1.50
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
30
40
presure side
50
X/C
60
70
80
90
100
Angle of attack = 20o
suction side
Cp
Cp
presure side
50
60
X/C
30
-1.00
-1.50
10
20
presure side
1.50
0
10
Angle of attack = 8o
suction side
1.50
Cp
Cp
presure side
50
X/C
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
X/C
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
Figure 14(a): Pressure Distribution over the aerofoil for angles of attack from 0 to 20 degree
16
90
100
presure side
Angle of attack = 24o
suction side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.50
Angle of attack = 28o
-1.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
100
-3.00
0
X/C
presure side
1.50
suction side
10
Angle of attack = 32o
20
30
40
presure side
50
X/C
60
70
80
90
100
Angle of attack =32o
suction side
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
Cp
Cp
suction side
-1.50
-2.00
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
50
X/C
60
70
80
90
0
100
10
Angle of attack =40o
suction side
20
30
40
50
60
X/C
presure side
1.50
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
Cp
Cp
presure side
1.50
Cp
Cp
1.50
-1.00
70
suction side
80
90
100
Angle of attack =44o
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
0
100
10
20
30
40
50
X/C
60
70
80
Figure 14(b): Pressure Distribution over the aerofoil for angles of attack from 24 to 44 degree
17
90
100
presure side
suction side
Angle of attack =48o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
50
X/C
60
70
80
90
0
100
Angle of attack =56o
suction side
10
20
30
40
presure side
1.00
1.50
50
X/C
60
70
suction side
80
90
100
Angle of attack =56o
0.50
1.00
0.00
0.00
-0.50
-0.50
-1.00
Cp
0.50
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
presure side
60
70
suction side
80
90
0
100
10
20
30
40
presure side
Angle of attack =60o
1.00
1.50
0.50
1.00
50
X/C
60
70
suction side
80
90
0.00
-0.50
-1.00
-1.50
-0.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
0
100
10
20
30
40
50
60
X/C
70
80
90
Figure 14(c): Pressure Distribution over the aerofoil for angles of attack from 48 to 72 degree
18
100
Angle of attack =72o
0.50
0.00
Cp
Cp
suction side Angle of attack =52o
-1.00
-1.50
Cp
presure side
1.50
Cp
Cp
1.50
100
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
X/C
Angle of attack =88o
suction side
presure side
1.50
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
Cp
Cp
40
50
60
70
80
90
100
X/C
presure side
-1.00
Angle of attack =92o
suction side
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
X/C
presure side
1.50
50
60
70
80
90
100
X/C
suction side
Angle of attack =96o
presure side
suction side
Angle of attack =100o
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
Cp
Cp
Angle of attack =84o
suction side
1.50
Cp
Cp
suction side Angle of attack =76o
presure side
1.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
10
20
30
40
50
60
70
80
X/C
Figure 14(d): Pressure Distribution over the aerofoil for angles of attack from 76 to 100 degree
19
90
100
Angle of attack =104o
suction side
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
Cp
Cp
presure side
1.50
-1.00
presure side
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
X/C
presure side
50
60
70
80
90
100
X/C
Angle of attack =112o
suction side
presure side
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
Cp
Cp
1.50
-1.00
Angle of attack =120o
suction side
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
50
X/C
60
suction side
70
80
90
0
100
Angle of attack =124o
10
20
30
40
50
60
70
80
90
100
X/C
1.50
1.50
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
suction side Angle of attack =128o
presure side
Cp
Cp
Angle of attack =108o
suction side
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
X/C
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
Figure 14(e): Pressure Distribution over the aerofoil for angles of attack from 104 to 128 degree
20
90
100
presure side
suction side
Angle of attack =132o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
presure side
50
X/C
60
70
80
90
100
0
0.50
0.00
-0.50
-0.50
-1.00
-1.00
Cp
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
20
30
40
50
30
40
presure side
60
70
60
70
80
90
suction side
80
90
100
Angle of attack =148o
-3.00
100
0
10
20
30
40
50
X/C
1.00
50
presure side
0.50
10
20
Angle of attack =144o
suction side
1.00
0
10
X/C
1.00
60
70
80
90
100
X/C
suction side
Angle of attack =152o
o
suction side Angle of attack =156
presure side
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =140o
suction side
-1.00
-1.50
-3.00
Cp
presure side
1.50
Cp
Cp
1.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
10
20
30
40
50
60
70
80
X/C
Figure 14(f): Pressure Distribution over the aerofoil for angles of attack from 132 to 156 degree
21
90
100
presure side
1.00
Angle of attack =160o
suction side
0.00
0.00
-0.50
Cp
Cp
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
50
X/C
60
suction side
70
80
90
0
100
Angle of attack =168o
10
20
30
40
50
X/C
presure side
1.00
1.00
60
70
80
90
100
suction sideAngle of attack =172o
0.50
0.50
0.00
0.00
-0.50
Cp
-0.50
Cp
suction side Angle of attack =164o
0.50
0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
presure side
1.00
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
suction side Angle of attack =176o
presure side
0.50
1.00
0.00
0.50
suction side
Angle of attack =180o
0.00
-0.50
-0.50
-1.00
Cp
Cp
presure side
1.00
-1.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
-3.00
100
0
10
20
30
40
50
X/C
60
70
80
Figure 14(g): Pressure Distribution over the aerofoil for angles of attack from 160 to 180 degree
22
90
100
presure side
1.00
suction side Angle of attack =184o
presure side
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
Cp
Cp
Angle of attack
=188o
suction side
1.00
-1.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
presure side
1.00
50
X/C
60
suction side
70
80
90
-3.00
100
0
Angle of attack =196o
10
20
30
40
presure side
50
X/C
60
suction side
70
80
90
100
Angle of attack =204o
1.00
0.50
0.50
0.00
0.00
-0.50
-1.00
Cp
Cp
-0.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
50
X/C
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
suction side
presure side
Angle of attack =208o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
-1.00
-1.50
-1.50
suction sideAngle of attack =212o
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
-3.00
100
0
10
20
30
40
50
X/C
60
70
80
Figure 14(h): Pressure Distribution over the aerofoil for angles of attack from 184 to 212 degree
23
90
100
suction side
Angle of attack =216o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
presure side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
60
suction side
70
80
90
suction side
0
Angle of attack =224o
10
20
30
40
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
50
X/C
60
suction side
70
80
90
100
Angle of attack =228o
-3.00
0
10
20
30
40
50
60
70
80
90
100
0
10
20
30
40
X/C
presure side
Angle of attack =232o
suction side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
X/C
50
60
70
80
90
100
X/C
Cp
Cp
Angle of attack =220o
-3.00
100
Cp
Cp
presure side
50
X/C
presure side
60
70
80
90
presure side
suction side
Angle of attack =236o
-3.00
100
0
10
20
30
40
50
X/C
60
70
80
Figure 14(i): Pressure Distribution over the aerofoil for angles of attack from 216 to 236 degree
24
90
100
presure side
suction side
Angle of attack =240o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
Angle of attack =244o
-1.00
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
1.00
50
X/C
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
suction side
Angle of attack =248o
presure side
1.00
suction side
Angle of attack =256o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
suction side
-1.50
-1.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
50
X/C
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
suction side
Angle of attack =260o
Angle of attack =264o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
Cp
-0.50
Cp
presure side
1.00
Cp
Cp
1.00
-1.00
-1.50
-1.00
presure side
-1.50
suction side
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
X/C
10
20
30
40
50
60
70
80
X/C
Figure 14(j): Pressure Distribution over the aerofoil for angles of attack from 240 to 264 degree
25
90
100
presure side
Angle of attack =268o
1.00
suction side
Angle of attack =272o
1.00
0.50
0.50
0.00
0.00
-0.50
presure side
-1.00
Cp
Cp
-0.50
suction side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
1.00
50
X/C
60
suction side
70
80
90
0
100
10
20
30
40
Angle of attack =276o
presure side
60
70
80
90
100
suction side
Angle of attack =280o
1.00
0.50
0.00
-0.50
-0.50
-1.00
-1.00
Cp
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
X/C
presure side
50
60
70
80
90
100
X/C
suction side
Angle of attack =284o
presure side
1.50
suction side
Angle of attack =288o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
Cp
Cp
50
X/C
0.50
Cp
-1.00
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
100
0
X/C
10
20
30
40
50
60
70
80
X/C
Figure 14(k): Pressure Distribution over the aerofoil for angles of attack from 268 to 288 degree
26
90
100
presure side
Angle of attack =292o
suction side
1.00
suction side
0.00
0.00
-0.50
Cp
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
40
X/C
presure side
50
60
70
80
90
100
X/C
presure side
Angle of attack =304o
suction side
suction side
Angle of attack =308o
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
40
X/C
presure side
50
60
70
80
90
100
X/C
suction side
Angle of attack =312o
presure side
1.00
1.00
suction side
Angle of attack =316o
0.50
0.50
0.00
0.00
-0.50
Cp
-0.50
Cp
Angle of attack =296o
0.50
0.50
Cp
presure side
1.00
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
Figure 14(l): Pressure Distribution over the aerofoil for angles of attack from 292 to 316 degree
27
90
100
presure side
Angle of attack =320o
suction side
suction side
0.00
0.00
-0.50
Cp
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
X/C
presure side
Angle of attack =328o
suction side
presure side
1.00
60
70
80
90
100
suction side
Angle of attack =332o
0.50
0.50
0.00
0.00
-0.50
Cp
-0.50
Cp
50
X/C
1.00
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
presure side
1.00
50
X/C
60
suction side
70
80
90
-3.00
100
0
Angle of attack =336o
10
20
30
40
50
presure side
1.00
60
X/C
70
suction side
80
90
100
Angle of attack =340o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =324o
0.50
0.50
Cp
presure side
1.00
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
0
100
10
20
30
40
50
X/C
60
70
80
\
Figure 14(m): Pressure Distribution over the aerofoil for angles of attack from 320 to 340 degree
28
90
100
presure side
1.00
suction side
Angle of attack =344o
suction side
0.00
-0.50
-1.00
-1.00
Cp
0.00
-0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
X/C
presure side
1.00
50
60
70
80
suction side
presure side
1.00
Angle of attack =352o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
100
suction side
Angle of attack =356o
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
presure side
1.00
40
50
X/C
60
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
suction side
Angle of attack =360o
0.50
0.00
-0.50
Cp
90
X/C
Cp
Cp
Angle of attack =348o
0.50
0.50
Cp
presure side
1.00
-1.00
-1.50
-2.00
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
100
X/C
Figure 14(n): Pressure Distribution over the aerofoil for angles of attack from 334 to 360 degree
29
90
100
2. Cp plot for variable angles of attack NWT 2004
presure side
1.00
suction side
Angle of attack = 0o
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
presure side
1.00
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
suction side
Angle of attack = 8o
0.00
-0.50
-0.50
-1.00
-1.00
Cp
0.50
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
presure side
1.00
0.50
suction side
Angle of attack = 16o
-3.00
0
10
20
30
40
50
X/C
presure side
1.50
60
70
suction side
80
90
100
0
Angle of attack = 20o
10
20
30
40
50
X/C
presure side
1.00
60
suction side
70
80
90
100
Angle of attack = 24o
0.50
1.00
0.50
0.00
0.00
-0.50
-0.50
-1.00
Cp
Cp
Angle of attack = 4o
suction side
0.50
0.50
Cp
presure side
1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.50
-3.00
0
10
20
30
40
X/C
50
60
70
80
90
0
100
20
40
60
80
X/C
Figure 15(a): Pressure Distribution over the aerofoil for angles of attack from 0 to 20 degree
30
100
presure side
1.00
Angle of attack = 28o
suction side
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
presure side
1.00
60
70
80
90
100
0
Angle of attack = 40o
suction side
10
20
30
40
50
X/C
presure side
1.00
0.50
60
70
80
90
100
Angle of attack = 44o
suction side
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack = 4o
suction side
0.50
0.00
Cp
Cp
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
presure side
10
20
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
40
50
X/C
presure side
Angle of attack = 44o
suction side
30
60
70
suction side
80
90
100
Angle of attack = 52o
-1.00
Cp
Cp
presure side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
100
-3.00
0
X/C
10
20
30
40
X/C
50
60
70
80
Figure 15(b): Pressure Distribution over the aerofoil for angles of attack from 28 to 52 degree
31
90
100
presure side
1.00
suction side
Angle of attack = 56o
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
presure side
1.00
50
X/C
60
70
80
90
0
100
10
20
Angle of attack = 64o
suction side
30
40
50
60
70
80
90
100
X/C
presure side
Angle of attack = 68o
suction side
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
Cp
Cp
Angle of attack = 60o
suction side
0.50
0.00
Cp
Cp
0.50
-1.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
presure side
40
50
X/C
60
70
80
90
-3.00
100
0
Angle of attack = 72o
suction side
10
20
30
40
presure side
1.00
1.00
50
X/C
60
70
80
90
100
Angle of attack = 76o
suction side
0.50
0.50
0.00
0.00
-0.50
Cp
-0.50
Cp
presure side
1.00
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
X/C
50
60
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
Figure 15(c): Pressure Distribution over the aerofoil for angles of attack from 56 to 76 degree
32
90
100
presure side
presure side
Angle of attack = 80o
suction side
1.00
0.00
0.00
-0.50
Cp
Cp
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
X/C
presure side
50
60
70
80
90
-3.00
100
0
10
20
Angle of attack = 100o
suction side
30
40
50
X/C
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack = 80o
0.50
0.50
-1.50
-1.50
-2.00
-2.00
60
70
suction side
80
90
100
Angle of attack = 116o
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
PRESURE SIDE
60
SUCTION SIDE
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
Angle of attack = 132o
presure side
suction side
Angle of attack = 148o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
CP
suction side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
X/C
50
60
70
80
90
0
100
10
20
30
40
X/C
50
60
70
80
Figure 15(d): Pressure Distribution over the aerofoil for angles of attack from 80 to 148 degree
33
90
100
suction side
Angle of attack = 164o
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
presure side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
X/C
presure side
1.00
60
70
80
90
-3.00
100
0
Angle of attack = 196o
suction side
20
30
40
50
X/C
presure side
60
70
80
90
100
Angle of attack = 200o
suction side
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
10
1.00
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
presure side
60
70
suction side
80
90
0
100
10
Angle of attack = 228o
20
30
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack = 180o
suction side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
40
50
X/C
60
suction side
70
80
90
100
Angle of attack = 232o
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
100
0
10
20
30
40
50
X/C
60
70
80
Figure 15(e): Pressure Distribution over the aerofoil for angles of attack from 164 to 232 degree
34
90
100
Angle of attack =236o
suction side
presure side
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
presure side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
40
presure side
1.00
50
X/C
60
70
80
90
-3.00
100
0
Angle of attack = 244o
suction side
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
X/C
presure side
60
suction side
70
80
90
20
30
40
presure side
50
X/C
60
70
suction side
80
90
100
Angle of attack = 248o
-3.00
100
0
10
20
Angle of attack = 252o
30
40
50
X/C
presure side
60
70
80
90
100
Angle of attack = 256o
suction side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
10
1.00
Cp
Cp
30
Angle of attack = 240o
suction side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
X/C
50
60
70
80
90
-3.00
100
0
10
20
30
40
X/C
50
60
70
80
Figure 15(f): Pressure Distribution over the aerofoil for angles of attack from 236 to 256 degree
35
90
100
o
suction side Angle of attack = 260
presure side
1.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
40
50
X/C
X/C
suction side
presure side
Angle of attack =268o
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
presure side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
60
70
suction side
80
90
100
Angle of attack =272 o
-3.00
-3.00
0
10
20
30
40
50
X/C
presure side
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
Angle of attack = 280o
suction side
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =264 o
suction side
0.50
0.50
Cp
presure side
1.00
-1.50
Angle of attack =288 o
suction side
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
10
20
30
40
50
X/C
60
70
80
90
Figure 15(g): Pressure Distribution over the aerofoil for angles of attack from 260 to 288 degree
36
100
presure side
1.00
suction side
presure side
Angle of attack = 292o
Angle of attack =296o
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
X/C
50
presure side
1.00
60
70
80
90
0
100
suction side Angle of attack = 300o
10
20
30
40
50
X/C
presure side
60
70
suction side
80
90
100
Angle of attack =304 o
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
suction side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
0
10
20
30
40 X/C
50
presure side
60
70
80
90
30
40
presure side
1.00
1.00
50
60
70
80
90
100
suction side
Angle of attack =312o
0.50
0.50
0.00
0.00
-0.50
Cp
-0.50
Cp
20
X/C
Angle of attack =308 o
suction side
10
100
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
10
20
30
40
50
X/C
60
70
80
Figure 15(h): Pressure Distribution over the aerofoil for angles of attack from 292 to 312 degree
37
90
100
presure side
1.00
suction side Angle of attack =316o
presure side
0.50
0.50
0.00
0.00
-0.50
-1.00
Cp
Cp
-0.50
-1.50
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
40
50
X/C
60
70
suction side
80
90
-3.00
100
0
10
Angle of attack =324o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.50
20
30
presure side
1.00
Cp
Cp
30
presure side
1.00
40
50
X/C
60
70
80
90
100
Angle of attack =328o
suction side
-1.00
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
presure side
suction side
10
20
30
40
50
X/C
presure side
Angle of attack =332o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =320 o
suction side
1.00
-1.50
60
70
80
90
100
suction side Angle of attack =336o
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
10
20
30
40
50
X/C
60
70
80
Figure 15(i): Pressure Distribution over the aerofoil for angles of attack from316 to 336 degree
38
90
100
presure side
1.00
suction side
Angle of attack =340o
0.50
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
100
0
10
20
30
X/C
suction side
Angle of attack =348o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
40
50
60
70
80
90
100
X/C
presure side
-1.50
-1.50
-2.00
-2.00
-2.50
presure side
suction side
Angle of attack =352o
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
X/C
presure side
suction side
40
50
X/C
presure side
Angle of attack =356o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =344o
suction side
0.50
0.00
Cp
Cp
presure side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
60
suction side
70
80
90
100
Angle of attack =360o
-3.00
0
10
20
30
40
50
60
70
80
90
100
0
X/C
10
20
30
40
X/C
50
60
70
80
Figure 15(k): Pressure Distribution over the aerofoil for angles of attack from 340 to 360 degree
39
90
100
3. Cp plot for variable angles attack NWT 2005
presure side
suction side
Angle of attack =0 o
presure side
1.00
1.00
0.50
0.50
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
Angle of attack =12o
suction side
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
presure side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
Angle of attack =16o
suction side
-3.00
0
10
20
30
40
presure side
50
X/C
60
70
80
90
0
100
10
20
Angle of attack =20o
suction side
30
40
50
X/C
60
70
80
90
100
suction side Angle of attack =24o
presure side
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =4 o
suction side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
0
100
10
20
30
40
50
X/C
60
70
80
Figure 16(a): Pressure Distribution over the aerofoil for angles of attack from 0 to 24 degree
40
90
100
presure side
suction side
Angle of attack =28o
presure side
1.00
1.00
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.50
-3.00
0
10
20
30
40
X/C
presure side
1.00
50
60
70
suction side
80
90
0
100
Angle of attack =36 o
20
30
40
50
X/C
presure side
60
70
suction side
80
90
100
Angle of attack =40 o
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
10
1.00
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
X/C
presure side
suction side
40
50
X/C
presure side
Angle of attack = 44o
1.00
60
70
80
90
100
suction side Angle of attack = 48o
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =32o
suction side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
X/C
50
60
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
Figure 16(b): Pressure Distribution over the aerofoil for angles of attack from 28 to 48 degree
41
90
100
Angle of attack = 52o
suction side
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
presure side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
presure side
suction side
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
40
X/C
presure side
1.00
Angle of attack = 60o
suction side
60
70
80
90
100
presure side
Angle of attack =64o
suction side
1.00
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
50
X/C
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
X/C
presure side
40
50
60
70
80
90
100
X/C
suction side
Angle of attack =68o
1.00
presure side
1.00
suction side
Angle of attack =72o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack = 56o
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
10
20
30
40
X/C
50
60
70
80
Figure 16(c): Pressure Distribution over the aerofoil for angles of attack from 52 to 72 degree
42
90
100
presure side
1.00
presure side
Angle of attack =76o
suction side
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
X/C
presure side
1.00
suction side
Angle of attack =84o
40
X/C
presure side
1.00
0.50
50
60
70
suction side
80
90
100
Angle of attack =88 o
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =80o
0.50
0.00
Cp
Cp
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
X/C
presure side
1.00
Angle of attack =92o
suction side
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
10
20
30
40
50
60
70
80
90
presure side
1.00
0.50
0
40
50
60
70
80
90
100
X/C
Cp
Cp
suction side
1.00
suction side
Angle of attack =100o
-3.00
100
0
X/C
10
20
30
40
50
60
70
80
X/C
Figure 16(d): Pressure Distribution over the aerofoil for angles of attack from 76 to 100 degree
43
90
100
presure side
1.00
suction side
Angle of attack =108o
0.50
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
10
20
30
40
50
60
70
80
90
100
0
10
20
30
X/C
presure side
40
50
60
70
80
90
100
X/C
suction side
presure side
Angle of attack =124o
1.00
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =116o
-3.00
0
-1.50
suction side
Angle of attack =128o
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
X/C
presure side
suction side
Angle of attack =136o
0.00
-0.50
-0.50
-1.00
-1.00
Cp
0.50
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
10
20
30
40
50
60
70
80
90
presure side
1.00
0.50
0
40
50
60
70
80
90
100
X/C
1.00
Cp
suction side
0.50
0.00
Cp
Cp
presure side
1.00
suction side Angle of attack = 140o
-3.00
100
0
X/C
10
20
30
40
50
60
70
80
X/C
Figure 16(f): Pressure Distribution over the aerofoil for angles of attack from 108 to 140 degree
44
90
100
presure side
1.00
suction side
Angle of attack = 144o
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
X/C
presure side
1.00
50
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
Angle of attack =152o
suction side
presure side
1.00
0.50
Angle of attack = 160o
suction side
0.50
0.00
-0.50
-0.50
-1.00
-1.00
Cp
0.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
10
20
30
X/C
presure side
1.00
40
50
60
70
80
90
100
X/C
suction side
Angle of attack =164o
presure side
1.00
0.50
suction side Angle of attack = 170o
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack =152o
suction side
0.50
0.50
Cp
presure side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
X/C
10
20
30
40
50
60
70
80
X/C
Figure 16(g): Pressure Distribution over the aerofoil for angles of attack from 144 to 170 degree
45
90
100
presure side
1.00
suction side
presure side
Angle of attack = 168o
0.00
-0.50
-0.50
Cp
Cp
0.00
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
X/C
presure side
1.00
50
60
70
80
90
0
100
10
20
30
40
50
60
70
80
90
100
X/C
suction side Angle of attack = 208o
presure side
1.00
0.50
Angle of attack =216o
suction side
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
Angle of attack = 200o
0.50
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
X/C
presure side
1.00
50
60
suction side
70
80
90
100
0
Angle of attack = 232o
10
20
30
40
50
X/C
presure side
1.00
60
70
suction side
80
90
100
Angle of attack = 240o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
suction side
1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
-3.00
0
10
20
30
40
50
60
70
80
90
0
100
X/C
10
20
30
40
50
60
70
80
X/C
Figure 16(h): Pressure Distribution over the aerofoil for angles of attack from 168 to 240 degree
46
90
100
presure side
suction side
Angle of attack = 248o
presure side
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
1.00
-1.50
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
X/C
presure side
1.00
suction side
Angle of attack =260o
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
40
50
X/C
presure side
1.00
Cp
Cp
Angle of attack =256o
-1.50
-2.00
60
70
suction side
80
90
100
Angle of attack =280o
-3.00
0
10
20
30
40
50
60
70
80
90
100
0
10
20
30
X/C
presure side
1.00
40
50
60
70
80
90
100
X/C
suction side
Angle of attack =288o
presure side
1.00
0.50
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
Cp
suction side
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
suction side
Angle of attack =304o
-3.00
0
10
20
30
40
50
X/C
60
70
80
90
100
0
10
20
30
40
X/C
50
60
70
80
Figure 16(i): Pressure Distribution over the aerofoil for angles of attack from 248 to 304 degree
47
90
100
presure side
1.00
suction side Angle of attack =312o
0.50
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
-3.00
0
10
20
30
40
50
60
70
80
90
-3.00
100
0
10
20
30
X/C
presure side
1.00
suction side
Angle of attack =332o
presure side
1.00
50
60
70
80
0.00
0.00
-0.50
-0.50
-1.00
-1.00
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
100
suction side
Angle of attack =336o
-3.00
-3.00
0
10
20
30
40
50
X/C
presure side
1.00
60
70
suction side
80
90
0
100
Angle of attack =344o
10
20
0.50
0.00
0.00
-0.50
-0.50
-1.00
-1.00
Cp
0.50
-1.50
-1.50
-2.00
-2.00
-2.50
-2.50
30
40
50
X/C
presure side
1.00
60
70
suction side
80
90
100
Angle of attack =352o
-3.00
-3.00
0
10
20
30
40
X/C
presure side
1.00
50
60
70
80
90
0
100
10
20
30
40
50
60
70
80
X/C
suction side
Angle of attack =360o
0.50
0.00
-0.50
Cp
90
0.50
Cp
Cp
40
X/C
0.50
Cp
Angle of attack =320o
suction side
0.50
0.00
Cp
Cp
presure side
1.00
-1.00
-1.50
-2.00
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Figure 16(j): Pressure Distribution over the aerofoil for angles of attack from 312 to 360 degree
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REPORT DOCUMENTATION PAGE
TITLE
Experimental characteristics of wind turbine blading
over full 0 to 360 degree angle of attack
352-(&7 NUMBER/DATE
5'5',$pirl 2014
AUTHOR(S)
A.P.Haran and S.Soundranayagam
PERFORMING ORGANIZATION/DEPARTMENTS
No. of copies
Department of Aeronautical engineering
PARK college of engineering and Technology
Anna university, Coimbatore
OTHER PARTICIPATING
ORGANIZATION/DEPARTMENTS
SPONSORING AGENCY AND ADDRESS
Centre for Wind Energy Technology- Chennai
(C-WET)
SUPPLEMENTARY NOTES
Centre for Wind Energy Technology
ABSTRACT
SPONSORING AGENCY
DISTRIBUTION/AVAILABILITY
STATEMENT
Unrestricted
A well designed wind turbine should have a good low speed starting characteristics and
an optimum performance at rated wind speed. This depends on the knowledge of the aerofoil
characteristics over 360 degree angle of attack and a detailed aerodynamic behavior of flow
around wind turbine aerofoils in the regions immediately before and after stall. It is also
necessary to detect the stall hysteresis, if any, in the chosen profiles. This report summarizes the
experimental work done on three wind turbine blade profiles designed by National Aerospace
Laboratories Bangalore for a given wind turbine power generation system. The 2D blades have
been manufactured with pressure tapings and tested at angles of attack varying from 0o to 360o to
generate pressure distribution in PARK airflow laboratory. Based on the pressure distribution,
aerodynamic characteristic viz. Cl and Cd have been estimated at a Reynolds number of 200 000
for all angles of attack ranging from 0o to 360o for the three profiles. Deep stall hysteresis has
been captured in all three cases. The results indicate that the wind turbine profiles have been
chosen to have a good starting characteristics and good performance at rated wind speed. The
operation of the turbine is such that it avoids regions having hysteresis.
SUBJECT TERMS