M. Herr > 01.10..2009
Measurement and Scaling of Trailing-Edge Noise*
Michaela Herr
Institute of Aerodynamics and Flow TechnologyDLR Braunschweig
13th CEAS-ASC Workshop and 4th Workshop of X3-Noise, “Resolving Uncertainties in Airframe Noise Testing and CAA
Validation”, Bucharest, Romania, 1-2 October 2009
*rather an extensive look at the scaling of the related source quantities
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
2
BackgroundPrimary goals
Set-up of an experimental database which is suitable for parametric trailing-edge (TE) noise source studies and for CAA validationImprove DLR’s TE noise measurement and prediction methods
With reference to the upcoming “Workshop on Benchmark Problems for Airframe Noise Computations-I” to be held on June 10-11, 2010
ApproachDefinition of a simple generic test setup in the Acoustic Wind-Tunnel Braunschweig (AWB) with a reduced set of parameters, including realistic (HLD) Reynolds numbersComparison with theoretical approaches and with other available test data to provide
Validation of the chosen measurement data correctionsEstimates of systematic uncertainty contributions
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Plate model0.15 mm
1 mm
Generic Test Setup - Acoustic Wind-Tunnel Braunschweig (AWB)
u
5 deglc
= 0.8–2.0 mu∞
= 40–60 m/sRe
= 2.1 Mio–7.9 Mio
= 0 deg
= 0 deg
LE tripping
Nozzle exit:0.8 m x 1.2 m
Exchangeable TE sections
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
4
Trailing-Edge Noise Data AssessmentMeasurement of related scaling parameters in the source region Measurement of the farfield TE noise; estimation of absolute levels
TBL mean velocity profiles and integral scales
Unsteady surface pressure point and cross spectra
Farfield TE noise spectra (re. unit distance and span)
Brooks & Hodgson (1981): )()1²(²2
)( 03
SMr
bMS
V
xV
00
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
5
Trailing-Edge Noise Data Assessment
TBL thickness wall friction velocity uw
/∞
, TBL edge velocity ue
Chase (1987):
Estimation of the surface pressure spectrum from TBL data
23
21 kkk
²21
212 k
ubVkk
|/²²|²
)(²)(²...................
...1|/²²|
²²
|/²²|)(
),(
22132
0
20
2
254
25
2
42/520
2
32
0
ckkkb
bkbkkbbb
ckkb
kckb
bkuP
k
Goody (2004), based on Howe (2000):
757.07.375.0
2
20
/1.15.0/
/3)/)((
ete
e
w
e
uRu
uuS
)//()/( 2 uuR et
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Part I – Measured TBL Mean Velocity Profiles Hot-wire (CTA) measurement resultsue
/u∞
= 0.98 ±
0.02 (40:1)
u =40, 50, 60 m/s
lc = 0.8 mlc = 1.2 mlc = 1.6 mlc = 2.0 m
x2, mm
u/u e
0 10 20 30 400
1
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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u =40, 50, 60 m/s
lc = 0.8 mlc = 1.2 mlc = 1.6 mlc = 2.0 m
x2+
u+
100 101 102 103 1040
10
20
30
40
u+ = x2+
u+ = 1/0.41 ln x2+ + 5
Scaling based on inner scale, ∞/u
);( 2 xf
uuu
uxx 22
u =40, 50, 60 m/s
lc = 0.8 mlc = 1.2 mlc = 1.6 mlc = 2.0 m
x2, mm
u/u e
0 10 20 30 400
1
Part I – Measured TBL Mean Velocity Profiles
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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u =40, 50, 60 m/s
lc = 0.8 mlc = 1.2 mlc = 1.6 mlc = 2.0 m
x2/99
u/u e
10-3 10-2 10-1 1000
1
u/ue = 0.084 ln(x2/99) + 0.82
Scaling based on outer scale,
);( *2xF
uuue
2*
2xx
u =40, 50, 60 m/s
lc = 0.8 mlc = 1.2 mlc = 1.6 mlc = 2.0 m
x2, mm
u/u e
0 10 20 30 400
1
Part I – Measured TBL Mean Velocity Profiles
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Part I – Derived ParametersReconstruction of the velocity profiles, Coles’ (1956) Law of the Wake
;)ln(1122
sin15.0)ln(1 22
B
uuxBxu e
x2, mm
u/u e
0 10 20 30 400
1
u =40 m/s50 m/s60 m/s
99
1
,, 2
, H12
uw
These are used in the following for the scaling of unsteady surface pressure and TE noise data.
/u
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Unsteady surface pressure point and cross spectra
Part II – Unsteady Surface Pressure Data
Farfield TE noise spectra (re. unit distance and span)
TBL mean velocity profiles and integral scales
Point PSD close to the TEStreamwise and spanwise coherence decayStreamwise and spanwise coherence lengthsConvection velocities
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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f, kHz
10lo
g(S
0(f)/
p2 ref)
=L p(
f=
1H
z),d
B
100 10160
65
70
75
80
85
90lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
Part II – Point PSDs close to the TE
TE
u∞
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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1/ue
10lo
g[S
0(
)ue/q
e2 1],
dB
10-1 100 101-65
-60
-55
-50
-45
-40
-35lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
f, kHz
10lo
g(S
0(f)/
p2 ref)
=L p(
f=
1H
z),d
B
100 10160
65
70
75
80
85
90lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
Part II – Point PSDs close to the TE Scaling based on outer scales:
Pressure scale: qe
= ½∞
ue2
Time scale: 1
/ue or 99
/ue
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Scaling based on “mixed” scalesPressure scale: w
=∞
u2Time scale: 1
/u
, 99
/u
, 1
/ue
, 99
/ue
Scaling based on inner scalesPressure scale: wTime scale: ∞
/u2
Part II – Point PSDs close to the TE
99/u
10lo
g[S
0(
)u/
w2 99
],dB
101 102 103-35
-30
-25
-20
-15
-10
-5lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
-0.8
0.3
-1
/u2
10lo
g[S
0(
)u2 /
w2 ],
dB
10-2 10-1 1000
5
10
15
20
25
30lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
/u2 = 0.3
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Part II – Current Prediction Models for point PSDs Chase (1987) model:
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
Chase (1987)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Part II – Current Prediction Models for point PSDs Chase (1987) model:
Empirical factors need a more detailed experimental assessment
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
Chase (1987)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
coefficientschanged acc.to Schewe (1993)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Part II – Current Prediction Models for point PSDs Goody (2004) model
RT = 123
RT = 51
Goody (2004)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Part II – Current Prediction Models for point PSDs Goody (2004) model
High frequency data corrections have to be taken with care!Existing deviations are due to application of high-frequency data corrections which seem to overvalue actual levels
RT = 123
RT = 51
Goody (2004)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
RT = 123
RT = 51
Goody (2004)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
18
Part II – Current Prediction Models for point PSDs Goody (2004) model
High frequency data corrections have to be taken with care!Existing deviations are due to application of high-frequency data corrections which seem to overvalue actual levels
A combination of both models might apply.
RT = 123
RT = 51
Goody (2004)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
RT = 123
RT = 51
Goody (2004)
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
RT = 123
RT = 51
combined approach
99/ue
10lo
g[S
0(
)ue/
w2 99
],dB
100 101 102-20
-15
-10
-5
0
5
10lc=0.8 mlc=1.2 mlc=1.6 mlc=2.0 m
u =40 m/s50 m/s60 m/s
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
19
Part II – Coherence Decay and Coherence LengthsCorcos’ (1963) similarity approach:
Streamwise
Spanwise
TE
u∞
3x
1x)()(
),( 3,1
ji
xijij SS
S
1111 ),(/),( xvxxxij kV
),(/ 1 xv Vk
Currently restricted to 2-m-plate only!
x1,3/V(x1, )
ij
0 5 10 15 200
0.2
0.4
0.6
0.8
1
x3 = 0.714
x1 = 0.16
3 mm 0.10
7 mm 0.2317,16 mm 0.56,0.52
|x1,3| = |x1,3|/99=
u = 60 m/s
20,23 mm 0.65,0.75
4 mm 0.13
),(/exp),(
),(/exp),(
1333
1111
xxxxij
xxxxij
V
V
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
20
Part II – Coherence Decay and Coherence LengthsCorcos’ (1963) similarity approach:
Streamwise
Spanwise
TE
u∞
3x
1x)()(
),( 3,1
ji
xijij SS
S
1111 ),(/),( xvxxxij kV
),(/ 1 xv Vk
Currently restricted to 2-m-plate only!
),(/exp),(
),(/exp),(
1333
1111
xxxxij
xxxxij
V
V
x1,3/V(x1, )
ij
0 5 10 15 200
0.2
0.4
0.6
0.8
1
x3 = 0.714x1 = 0.17
3 mm 0.10
7 mm 0.2217,16 mm 0.54,0.51
|x1,3| = |x1,3|/99=
u = 50 m/s
20,23 mm 0.64,0.73
4 mm 0.13
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
21
Part II – Coherence Decay and Coherence LengthsCorcos’ (1963) similarity approach:
Streamwise
Spanwise
TE
u∞
3x
1x)()(
),( 3,1
ji
xijij SS
S
1111 ),(/),( xvxxxij kV
),(/ 1 xv Vk
Currently restricted to 2-m-plate only!
),(/exp),(
),(/exp),(
1333
1111
xxxxij
xxxxij
V
V
x1,3/V(x1, )
ij
0 5 10 15 200
0.2
0.4
0.6
0.8
1
x3 = 0.714x1 = 0.19
3 mm 0.09
7 mm 0.2217,16 mm 0.53,0.50
|x1,3| = |x1,3|/99=
u = 40 m/s
20,23 mm 0.62,0.71
4 mm 0.12
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
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Part II – Coherence Decay and Coherence Lengths
x1
x3
f(peak)
f, kHz
x1,
3/99
5 10 15
0.5
1
1.52
2.5u =40 m/s50 m/s60 m/s
333
111
//1//1
xvxx
xvxx
VkVk
Currently restricted to 2-m-plate only!
Assuming a constant V
0.65 u∞
Streamwise
Spanwise
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
23
Farfield TE noise spectra (re. unit distance and span)
Part III – Farfield TE Noise Data
TBL mean velocity profiles and integral scales
Unsteady surface pressure point and cross spectra
Absolute 1/3-octave band SPL re 1m span and 1m observer distance
Brooks & Hodgson (1981): )()1²(²2
)( 03
SMr
bMS
V
xV
00
¼``- Microphone
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
24
Estimation of absolute levels (re 1m span and 1m observer distance) requires extensive data corrections, as shown in the following…
Part III – Farfield TE Noise DataPrediction from the surface pressure data, assuming constant V
0.65 u∞
Currently restricted to 2-m-plate only!
fm, kHz
L p(1/
3),d
B
2 4 6 8 1030
40
50
60
70
80
90
100
u =40 m/s50 m/s60 m/s
Surface Pressure Kulite Data
FF TE Noise Mirror Data
fm, kHz
L p(1/
3),d
B
2 4 6 8 1030
40
50
60
70
80
90
100
u =40 m/s50 m/s60 m/s
Surface Pressure Kulite Data
FF TE Noise PredictionFF TE Noise Mirror Data
fm, kHz
L p(1/
3),d
B
2 4 6 8 1030
40
50
60
70
80
90
100
u =40 m/s50 m/s60 m/s
Surface Pressure Kulite Data
Brooks & Hodgson (1981): )()1²(²2
)( 03
SMr
bMS
V
xV
00
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
25
Part III – Elliptic Mirror SetupElliptic mirror specifics:
Focal distance: 1.15 mReflector diameter D = 1.4 mResolution width Aperture: 63 deg
Data correction for:Background noise (S/N
3 dB)
Sound wave convectionFrequency response function (gain, resolution)Shear layer refraction/scattering
¼``- Microphone
x
y
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
26
Part III – Elliptic Mirror SetupCorrection for frequency response (Schlinker, 1977)
21 )(2)(
JH
DRcxfD
3
2/
2/ 3
22
)(b
b
M
dxH
bGp
p
fm, kHz
L p(1
/3)co
rrec
tion,
dB
5 10 15 20
-40
-30
-20
-10
0
10
gain correctionresolution correctiontotal correction
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
27
Part III – Effect of Data Corrections1.6-m plate model with blunt TE (h = 1 mm)Focusing measurement techniques must be used because TE noise is buried by the tunnel self-noise!
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrected
empty test section
u= 60 m/s
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrectedLp (1/3) M
empty test section
u= 60 m/s
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrectedLp (1/3) MLp (1/3) M, shear-layer corrected
empty test section
u= 60 m/s
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrectedLp (1/3) MLp (1/3) M, shear-layer correctedLp (1/3) TE (b = 1 m)
empty test section
u= 60 m/s
mirror focus at TE
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
farfield mic. plate airfoilfarfield mic. BGNmirror mic. plate airfoil TE
u= 60 m/sb = 1.2 mr = 1.15 m(origin at TE, midspan)
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
28
Part III – Effect of Data Corrections1.6-m plate model with blunt TE (h = 1 mm)Focusing measurement techniques must be used because TE noise is buried by the tunnel self-noise!“Validation” of the procedure by alternative measurement techniques: COP
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrected
empty test section
u= 60 m/s
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrectedLp (1/3) M
empty test section
u= 60 m/s
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrectedLp (1/3) MLp (1/3) M, shear-layer corrected
empty test section
u= 60 m/s
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
uncorrectedLp (1/3) MLp (1/3) M, shear-layer correctedLp (1/3) TE (b = 1 m)
empty test section
u= 60 m/s
mirror focus at TE
fm, kHz
L p(1
/3),
dB
5 10 15 2030
40
50
60
70
80
farfield mic. plate airfoilfarfield mic. BGNmirror mic. plate airfoil TE
u= 60 m/sb = 1.2 mr = 1.15 m(origin at TE, midspan)
fm, kHz
L p(1
/3),
dB
5 10 15 2020
30
40
50
60
70
directional microphoneCOP
u= 40 m/s
b = 1.2 m
u= 60 m/s
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
29
fm/u
L p(1/
3)no
rm,d
B
0.1 1100
110
120
130
AWB (h = 0.15 mm)
Lp(1/3)norm= Lp(1/3)- 10 log (M5b/ r2)
u=40 m/s50 m/s60 m/s
fm/u
L p(1/
3)no
rm,d
B
0.1 1100
110
120
130
AWB (h = 0.15 mm)
Lp(1/3)norm= Lp(1/3)- 10 log (M5b/ r2)
u=40 m/s50 m/s60 m/s
BPM, sharp TE
Part III – Comparisons with Published TE Noise Data NACA0012 data by Brooks et al. (1986): COP semi-empirical prediction method (BPM, NAFNoise)
18 deg
0.4-m 2D-”NACA0012” with varying TE thickness
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
30
fm/u
L p(1/
3)no
rm,d
B
0.1 1100
110
120
130
AWB (h = 0.15 mm)
Lp(1/3)norm= Lp(1/3)- 10 log (M5b/ r2)
u=40 m/s50 m/s60 m/s
fm/u
L p(1/
3)no
rm,d
B
0.1 1100
110
120
130
AWB (h = 0.15 mm)
Lp(1/3)norm= Lp(1/3)- 10 log (M5b/ r2)
u=40 m/s50 m/s60 m/s
BPM, sharp TE
Part III – Comparisons with Published TE Noise Data NACA0012 data by Herrig et al.(2008): CPV 18 deg
0.4-m 2D-”NACA0012” with varying TE thickness
fm/u
L p(1/
3)no
rm,d
B
0.1 1100
110
120
130
AWB (h = 0.15 mm)AWB (h = 1 mm)
Lp(1/3)norm= Lp(1/3)- 10 log (M5b/ r2)
u=40 m/s50 m/s60 m/s
fm/u
L p(1/
3)no
rm,d
B
0.1 1100
110
120
130
AWB (h = 0.15 mm)AWB (h = 1 mm)
Lp(1/3)norm= Lp(1/3)- 10 log (M5b/ r2)
u=40 m/s50 m/s60 m/sHerrig et al.
(h = 1 mm)
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
31
Conclusions Presentation of a parametric plate model TE noise data set which (with the limitation to nonzero angles-of-attack and =
= /2) could
help to validate current CAA approaches, maximum Re
of 7.9 MioExcellent agreement of the plate model data set with theoretical modelsFair agreement with published data sets as derived at comparable but not identical test conditions (e.g. zero-pressure gradient surface pressure data covered by the Goody model), estimation of absolute TE noise levels was cross-checked by comparisons of additional NACA0012 measurement results with available NACA0012 dataLiterature review: Considerable uncertainty with regard to the measurement of farfield TE noise and its related source quantities prevails even for very simple generic test configurations Need of benchmarks for TE noise measurement (with major focus on the necessary frequency response corrections and facility-related effects) to provide the necessary data quality for CAA validation
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
32
Outlook Conduct RANS/CAA based predictions (PIANO-RPM) for the presented plate model experiment
respective RANS/CAA based predictions for a NACA0012, (published in Ewert et al., AIAA 2009-3269) were promising
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
33
Outlook Conduct RANS/CAA based predictions (PIANO-RPM) for the presented plate model experiment
respective RANS/CAA based predictions for a NACA0012, (published in Ewert et al., AIAA 2009-3269) were promising
Detailed comparison of directional microphone data with corresponding microphone array data
NACA0012 data available, but not yet analysedNumerical simulation of the mirror system transfer function (including shear-layer effects)Still open questions: determination of the various empirical coefficients in existing surface pressure models, estimation of based on mean TBL velocity profiles
See you in June 10-11, 2010 at the “Workshop on Benchmark Problems for Airframe Noise Computations-I”?
),( 1 xV
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
34
Thank you for your attention!
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
35
Appendix
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
36
Part II – Convection velocity
TE
u∞
3x
1x
1111 ),(/),( xvxxxij kV ),(/ 1 xv Vk
Currently restricted to 2-m-plate only!
(99/u)peak
Eq. 5.2
99/u
V(
x1,
)/u
200 400 600 800
0.4
0.6
0.8
1
1.2 u =40 m/s50 m/s60 m/s
(99/u)peak
99/u
V(
x1,
)/u
200 400 600 800
0.4
0.6
0.8
1
1.2
3 mm 0.17 mm 0.2
20 mm 0.6-0.7|x1| = |x1|/99=
u =40 m/s50 m/s60 m/s
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
37
Part III – Elliptic Mirror Setup
fm, kHz
SP
L 1/3
Cor
rect
ion,
dB
5 10 15 200
1
2
3
4
5
Position 2Position 3Position 4
Shear-layer effect at:
Shear-layer correction from comparative measurements at different x- positions, re Position 1
x
z
x
y1 2 3 4
CEAS-ASC/ X3-Noise Workshop 2009, Bucharest, (Romania) > M. Herr > 01.10.2009
38
Part III – Elliptic Mirror SetupMeasured “point source” frequency response function (Dobrzynski et al.,1998)
fm, kHz
w,1
0-3
m
10 20 30 40
20
40
60
80100
u∞=0 m/s40 m/s50 m/s60 m/s
theoretical prediction
��
�
� ��
������
�����������
fm, kHz
G,d
B
10 20 30 40
20
25
30
35
40
45u∞ =0 m/s40 m/s50 m/s60 m/s
theoretical prediction
η
H(η
),d
B
-2 0 2 4 6
-10
-5
0
fm = 2.5 kHzfm = 5 kHzfm = 10 kHz
Eq. 2.17�
� �
����� ���� �� ����
��
��21 )(2)(
JH