ewea annual event 2013 vienna february, 4-7, 2013
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EWEA Annual Event 2013 Vienna February, 4-7, 2013. - PowerPoint PPT PresentationTRANSCRIPT
Analysis of Vortex-induced Vibrations using a free-wake aeroelastic tool
Spyros Voutsinas (*)Fangmao Zou(**), Vasilis Riziotis(*), Jun Wang(***) (*) NTUA, School of Mechanical Engineering, Greece
(**) China-EU Institute for Clean and Renewable Energy, Wuhan, China
(***) Huazhong University of Science and Technology, Wuhan, China
EWEA Annual Event 2013Vienna
February, 4-7, 2013
Vortex induced vibrations 2/16
Vortex-induced vibrations & wind turbines
Aeroelastic instabilities and vortex-induced vibrations can appear on wind turbine blades at stand still.
1. Negative (CL-a) slope a~90o triggers Aeroelastic instabilities
2. Large vortex structures trigger Vortex induced vibrations
Du96-w-180: Skrzypiński et al, DTU 2012
Vortex induced vibrations 3/16
Validation
0.2 m
Good agreement in the prediction of the lift slope, critical for aeroelastic damping characterization
Finite:
The double wake model
Clmax Cdmax
v+, P-
v-, P+
ClminCdmax
v-, P+
v+, P-
Vortex induced vibrations 4/16
PSD of CL PSD of CD
0.05 m
0.20 m
0.115 hzf =0.23 hzf =
0.10 hzf = 0.20 hzf =
about 10% shift in vortex shedding frequencyf
PSD of CL PSD of CD
Validation
Vortex induced vibrations 5/16
Forced vibration results
max appears at vibration periods 9.7 or 9.8 which are close to the
vortex shedding period 10.
𝑨∗
𝑻 ∗= 𝑨𝑻𝑽 = 𝑨𝝎
𝟐𝝅𝑽 =𝑼𝒎𝒂𝒙
𝟐𝝅𝑽 = 𝟏𝟐𝝅 ∙ 𝐭𝐚𝐧 𝜷𝒎𝒂𝒙
Cl time series with different A*/T*, α=90
- curve of different A*/T*
𝒇 𝒗=𝟎 .𝟏𝐇𝐳
Vortex induced vibrations 6/16
(d) T*=10 (e) T*=11 (f) T*=13
(a) (b) (c)
Cl-x plot of A*/T*=0.03 series
Forced vibration results
Vortex induced vibrations 7/16
V
w
u
Structural model with 3 d.o.f.
𝜃
u: edgewise displacement
w: flapwise displacement𝜃: torsional angle
k: spring coefficient
: the distance between
the gravity center and the
elastic axis
V: inflow velocity
Aeroelastic simulations
Typical blade section model
Vortex induced vibrations 8/16
angle of attack [deg]
dam
ping
inlo
gde
crem
ent[
%]
50 60 70 80 90 100 110 120 1300
1
2
3
4
5
angle of attack [deg]
dam
ping
inlo
gde
crem
ent[
%]
50 60 70 80 90 100 110 120 13040
50
60
70
80
Aeroelastic simulationseigenvalue stability analysis
m=165 kg/m, fflap =0.7 hz, fedge =1.1 hz
c=2.8 m (r/R=0.7), d=1.25% (=0.2%)
high damping of flap mode driven by high CD value
flap mode
edge mode
damping of edge mode driven by negative slope of
CL and CD value
wind speed 25 m/s
LDdCCd
damping driving parameter
Vortex induced vibrations 9/16
angle of attack [deg]
dam
ping
inlo
gde
crem
ent[
%]
50 60 70 80 90 100 110 120 130-6
-4
-2
0
2
4
6 2D CD (CDmax=2.0)3D CD (CDmax=1.3)
Aeroelastic simulationseigenvalue stability analysis: reference to “reality”
3D aerodynamic characteristics
m=165 kg/m, fflap =0.7 hz, fedge =1.1 hz
c=2.8 m (r/R=0.7), d=1.25% (=0.2%)
edge mode
wind speed 25 m/s
LDdCCd
damping driving parameter
DmaxC 1.3
Vortex induced vibrations 10/16
Aeroelastic simulations
eigenvalue stability analysis – effect of mass and chord length
angle of attack [deg]
dam
ping
inlo
gde
crem
ent[
%]
50 60 70 80 90 100 110 120 1300
1
2
3
4
5
6
7
8 Rf=0.021Rf=0.042Rf=0.024
fR c / m= wind speed 25 m/s
angle of attack [deg]
dam
ping
inlo
gde
crem
ent[
%]
50 60 70 80 90 100 110 120 130-8
-6
-4
-2
0Rf=0.021 (CDmax=1.3)Rf=0.024 (CDmax=1.3)
C=2.8C=1.6
Vortex induced vibrations 11/16
Aeroelastic simulations
eigenvalue stability analysis – effect of structural properties
m=165 kg/m, c=2.8 m: (Rf=0.021)
wind speed 25 m/s
angle of attack [deg]
dam
ping
inlo
gde
crem
ent[
%]
50 60 70 80 90 100 110 120 130-8
-6
-4
-2
0 fedge=1.1hzfedge=0.9 hzfedge=0.8 hz
angle of attack [deg]
dam
ping
inlo
gde
crem
ent[
%]
50 60 70 80 90 100 110 120 130-8
-6
-4
-2
0
2
4 0 deg5 deg10 deg-5 deg-10 deg
structural pitchEdge frequency
fflap =0.7 hz, fedge =1.1 hz
Vortex induced vibrations 12/16
Aeroelastic simulationsnon-linear aeroelastic stability analysis
time [s]
edge
wis
ede
flect
ion
[m]
50 100 150
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
m=165 kg/m, c=2.8 m (Rf=0.021)
wind speed 25 m/s
fflap =0.7 hz, fedge =1.1 hz
10s excitation period at the frequency of the edge mode (1.1
hz)
Strongly non linear behaviour. Difficult to measure damping aoa = 90o
angle of attack [deg]
liftc
oeffi
cien
tCL
40 60 80 100 120 140-1
-0.5
0
0.5
1unsteadysteady-state (mean CL)
Vortex induced vibrations 13/16
Aeroelastic simulationsnon-linear aeroelastic stability analysis
m=165 kg/m, c=2.8 m (Rf=0.021)
wind speed 25 m/s
fflap =0.7 hz, fedge =1.1 hz
time [s]
ed
gew
ise
deflectio
n[m
]
20 30 40 50
-4
-2
0
2
4 aoa = 100o
angle of attack [deg]
liftc
oeffi
cien
tCL
40 60 80 100 120 140
-1
0
1
2unsteadysteady-state (mean CL)
Vortex induced vibrations 14/16
time [s]
flapw
ise
defle
ctio
n[m
]
40 50 60 70 80 90 100-1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
time [s]
edge
wis
ede
flect
ion
[m]
40 50 60 70 80 90 100-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
time [s]
flapw
ise
defle
ctio
n[m
]
40 50 60 70 80 90 100-1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
time [s]
edge
wis
ede
flect
ion
[m]
40 50 60 70 80 90 100-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
Aeroelastic simulationsanalysis of lock-in due to vortex shedding
time [s]
flapw
ise
defle
ctio
n[m
]
40 50 60 70 80 90 100-1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
time [s]
edge
wis
ede
flect
ion
[m]
40 50 60 70 80 90 100-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
m=165 kg/m, c=2.8 m (Rf=0.021)
fflap =0.7 hz, fedge =1.1 hz
U=10 m/s
U=15 m/s
U=20 m/s
fs1=0.36hz fs2=0.71hz
fs1=0.54hz fs2=1.07hz
fs1=0.71hz fs2=1.43hz
Vortex induced vibrations 15/16
time [s]
edge
wis
ede
flect
ion
[m]
40 50 60 70 80 90 100-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
Aeroelastic simulationsanalysis of lock-in due to vortex shedding
m=165 kg/m, c=2.8 m (Rf=0.021)
fflap =0.7 hz, fedge =1.1 hz
time [s]
flapw
ise
defle
ctio
n[m
]
40 50 60 70 80 90 100-1
-0.75
-0.5
-0.25
0
0.25
0.5
0.75
1
time [s]
flapw
ise
defle
ctio
n[m
]
20 30 40 50 60 70 80-2
-1
0
1
2
3
4
5
time [s]ed
gew
ise
defle
ctio
n[m
]
20 30 40 50 60 70 80-10-8-6-4-202468
10
time [s]
flapw
ise
defle
ctio
n[m
]
20 30 40 50 60 70-3
-2
-1
0
1
2
3
4
5
6
time [s]
edge
wis
ede
flect
ion
[m]
20 30 40 50 60 70 80
-10
-5
0
5
10
U=25 m/s
U=30 m/s
U=35 m/s
fs1=0.89hz fs2=1.79hz
fs1=1.07hz fs2=2.14hz
fs1=1.25hz fs2=2.50hz
Vortex induced vibrations 16/16
Conclusions
• The double wake model has been successfully applied • The cut-off length acts as calibration parameter. Good results were obtained
for relatively large values• Lock-in was detected at the shedding frequency corresponding to T~10. • The positive feedback between the lock-in phenomenon and the structural
vibration is found to be the main reason for the vortex induced aero-elastic instability.
Vortex induced vibrations 17/16
Thanks for your attention
END
Vortex induced vibrations 18/16
Aeroelastic simulationsanalysis of lock-in due to vortex shedding
m=165 kg/m, c=2.8 m (Rf=0.021)
fflap =0.7 hz, fedge =1.1 hz
flapwise deflection
flap deflection
edgewise deflection