National Aeronautics and Space Administration
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Jet-Surface Interaction – High Aspect Ratio Nozzle Test
Test Summary
Cliff Brown *
NASA Glenn Research Center
April 20, 2016
1
https://ntrs.nasa.gov/search.jsp?R=20160014889 2020-06-26T02:54:43+00:00Z
National Aeronautics and Space Administration
www.nasa.gov
Jet-Surface Interaction Noise Test Programs
2
JSI1044 (2015)
JSI-HAR (2015)
(TBD)(TBD)
Multi-Stream
Asp
ect
Rat
io
JSIT (2011-
2013)
ERN(2013)
/JSIT(2013)
JSI1044 (2015)
JSI1044 (2015)
* Covered by AATT and CST Projects
National Aeronautics and Space Administration
www.nasa.gov
Motivation:
Turbo-electric Distributed Propulsion Concept (TeDP)
• 32:1 aspect ratio slot
• Divided into 2:1 at exit
• Electric fan has low pressure ratio, low temperature ratio
• Aft deck extends (estimated) 1-4 slot heights downstream
3
Superconducting
Turbogenerators
Asymmetric Flow Path
* Kim et. al., AIAA 2015-3805
National Aeronautics and Space Administration
www.nasa.gov
Goals for JSI-HAR
1. Extend current database to larger aspect ratio nozzles
2. Verify / connect current small-scale database to larger-scale
rectangular nozzles near surfaces
3. Acquire data suitable for creating / validating empirical jet-
surface interaction noise models
4. Investigate the effect of nozzle septa on the jet-mixing and jet-
surface interaction noise sources
4
National Aeronautics and Space Administration
www.nasa.gov
Test Plan
1. Design and test 3 nozzles (listed by priority):
1. 16:1 aspect ratio – extend current database to higher aspect ratios
2. 8:1 aspect ratio – verify/connect small-scale database to larger-scale
3. 12:1 aspect ratio – midpoint to allow a second-order modeling
5
16:1 8:1 12:1
National Aeronautics and Space Administration
www.nasa.gov
Test Plan
1. Design and test 3 nozzles (listed by priority):
1. 16:1 aspect ratio – extend current database to higher aspect ratios
2. 8:1 aspect ratio – verify/connect small-scale database to larger-scale
3. 12:1 aspect ratio – midpoint to allow a second-order modeling
6
16:1 8:1 12:1
National Aeronautics and Space Administration
www.nasa.gov
Test Plan
1. Design and test 16:1, 8:1, 12:1 aspect ratio nozzles
2. Add aft decks / surfaces onto nozzles
1. Acquire data for modeling JSI source and shielding effect
7
National Aeronautics and Space Administration
www.nasa.gov
Test Plan
8“Open”
2:1 / 7 septa 1:1 / 15 septa
1. Design and test 16:1, 8:1, 12:1 aspect ratio nozzles
2. Add aft decks / surfaces onto nozzles
3. Design and test nozzle septa inserts
1. “Open” no septa insert – effect of aspect ratio on jet mixing noise
2. 2:1 / 7 septa inserts – similar to the TeDP concept
3. 1:1 / 15 septa insert – effect of varying number of septa
4. Other variations
National Aeronautics and Space Administration
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16:1 Nozzle Design
• Significant vorticity near corners
• Attached flow along outboard edge of major
axis (BL thickness still significant)
• No normal shocks at nozzle exit
• Continuous area contraction helps
• Significant wake from center vane (added
for structural support)
9
Axial Velocity
Vorticity
* Brown & Dippold, TWG Fall 2015
* Dippold, V., “Design and Analyses of High Aspect Ratio
Nozzle for Distributed Propulsion Acoustics
Measurements”, AIAA Aviation 2016 Conference
National Aeronautics and Space Administration
www.nasa.gov
6 8 10 12 1412
14
16
18
20
22
24
26
28
Flow Profile at Nozzle Exit
• 2:1 / 7 septa insert installed for
JSI-HAR but not in WIND-US
• Total pressure measured 0.25”
downstream of nozzle exit
• No indication of vortex in JSI-HAR
– 1 Hz averaged pressure data would not
likely pick this up even if present
• Flat profile between septa
• Losses slightly higher in JSI-HAR
data
10
P0
(lbf/
in2)
Position (in)
Septa wake (no
septa in CFD)
WIND-US
JSI-HAR
Ma=0.9, Unheated16:1 w/ 2:1 septa
National Aeronautics and Space Administration
www.nasa.gov
Goals for JSI-HAR
1. Extend current database to larger aspect ratio nozzles
2. Verify / connect current small-scale database to larger-scale
rectangular nozzles near surfaces
3. Acquire data suitable for creating / validating empirical jet-
surface interaction noise models
4. Investigate the effect of nozzle septa on the jet-mixing and jet-
surface interaction noise sources
11
National Aeronautics and Space Administration
www.nasa.gov
• Compare spectra to:
– Show effect of nozzle aspect ratio
– Connect to existing database via trends
• Similar to TeDP jet exit condition
– Mach 0.7, unheated
• Nozzles with different sizes
– 2:1, 4:1, 8:1 -> Area = 3.57 in2
– 16:1 -> Area = 33.7 in2
• Scale:
– Frequency as Strouhal number based
on nozzle height
– Distance to 100 equivalent jet diameter
• Trends follow from small to large
scale across test programs12
Sth
PS
D (
dB
)
10-1
100
101
60
65
70
75
80
85
902:1
4:1
8:1
16:1
187271873218707
275
Sth
PS
D (
dB
)
10-1
100
101
60
65
70
75
80
85
90
95
1002:1
4:1
8:1
16:1
187271873218707
275
Sth
PS
D (
dB
)P
SD
(d
B)
Θ=90º
Θ=150º
2:1
4:1
8:1
16:1
Extend to Higher Aspect Ratios
National Aeronautics and Space Administration
www.nasa.gov
Goals for JSI-HAR
1. Extend current database to larger aspect ratio nozzles
2. Verify / connect current small-scale database to larger-scale
rectangular nozzles near surfaces
3. Acquire data suitable for creating / validating empirical jet-
surface interaction noise models
4. Investigate the effect of nozzle septa on the jet-mixing and jet-
surface interaction noise sources
13
National Aeronautics and Space Administration
www.nasa.gov
Jet-Surface Interaction (JSI) Noise Sources and Effects
• Measured far-field noise includes:
– Jet-surface interaction noise sources
– Jet mixing noise (isolated)
– Shielding/Reflecting effect
• Types of JSI noise sources
– Surface loading (“scrubbing”) noise
– Trailing edge (“scattering”) noise
– Surface vibration noise
• Data acquired for surface lengths
xE/h = 0.83, 2, 4, 6, 8, zero standoff
14
JSI Source
Reflecting Effect
Shielding
Effect
StDj
Jet Mixing
Noise
1/1
2 O
ctav
e P
SD
(dB
)
Ground Observer
National Aeronautics and Space Administration
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Sth
PS
D (
dB
)
10-1
100
101
102
50
60
70
80
90
100
1102:1
8:1
16:1
1653916857
300
Sth
PS
D (
dB
)
10-1
100
101
102
50
60
70
80
90
100
1102:1
8:1
16:1
1653916857
300
• Compare spectra to:
– Effect surface at increase aspect ratios
– Connect to existing database via trends
• Similar to TeDP jet exit condition
– Mach 0.7, unheated
• Surface length, xE/h = 6
• Scale:
– Frequency as Strouhal number based
on nozzle height
– Distance to 100 equivalent jet diameter
• Trends follow from small to large
scale across test programs
15
Sth
PS
D (
dB
)P
SD
(d
B)
Θ=90º
Θ=150º
2:1
8:1
16:1
Extend to Larger Scale
National Aeronautics and Space Administration
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Sth
PS
D (
dB
)
10-1
100
101
102
50
60
70
80
90
100x
E/h = 9.5
Isolated
306282
Sth
PS
D (
dB
)
10-1
100
101
102
50
60
70
80
90
100x
E/h = 9.5
Isolated
306282
• Compare spectra to:
– Show effect of adding surface
• Similar to TeDP jet exit condition
– Mach 0.7, unheated
• Aspect ratio 16:1
• Surface length, xE = 8h
• JSI source maybe large relative to
shielding
• Model to full-scale factor matters
16
Sth
PS
D (
dB
)P
SD
(d
B)
Θ=90º
Θ=150º
xE/h=8
Isolated
Noise Impact of Surface
National Aeronautics and Space Administration
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Sth
PS
D (
dB
)
10-1
100
101
102
50
60
70
80
90
100
282288294300
282288294300306275
Sth
PS
D (
dB
)
10-1
100
101
102
50
60
70
80
90
100
110
282288294300
282288294300306275
• Compare spectra to:
– Show effect of surface length
• Similar to TeDP jet exit condition
– Mach 0.7, unheated
• Aspect ratio 16:1
• Shorter surface may give high
frequency shielding with smaller low
frequency penalty at 90º
• All surfaces produce more high
frequency noise than isolated at
150º
17
Sth
PS
D (
dB
)P
SD
(d
B)
Θ=90º
Θ=150º
Noise Impact of Surface Length
xE/h=0.83
xE/h=2
xE/h=4
xE/h=6
xE/h=8
Isolated
National Aeronautics and Space Administration
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Sth
PS
D (
dB
)
10-1
100
101
102
50
55
60
65
70
75
80
85
90
95
100S000
S030
S060
S090
294318362337
Sth
PS
D (
dB
)
10-1
100
101
102
50
60
70
80
90
100
294318362337
• Compare spectra to:
– Show effect sideline
• Similar to TeDP jet exit condition
– Mach 0.7, unheated
• 16:1, xE/h = 4
• Significant changes at downstream
observer angles as azimuthal angle
changes
18
Sth
PS
D (
dB
)P
SD
(d
B)
Θ=90º
Θ=150º
Noise Impact of Observer Azimuthal Angle
National Aeronautics and Space Administration
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Sth
PS
D (
dB
)
10-1
100
101
102
50
55
60
65
70
75
80
85
90I161
I16A
I16B
275393111
Sth
PS
D (
dB
)
10-1
100
101
102
50
55
60
65
70
75
80
85
90I161
I16A
I16B
269466100
• Compare spectra to:
– Show effect nozzle septa
• Similar to TeDP jet exit condition
– Mach 0.7, unheated
• 16:1, no surface
• Septa create tone to major axis
observer that grows with number of
septa
19
Sth
PS
D (
dB
)P
SD
(d
B)
Θ=90º
Θ=90º
Noise Impact of Nozzle Septa8:1 / 1
2:1 / 7
1:1 / 15
National Aeronautics and Space Administration
www.nasa.gov
Summary of JSI-HAR
1. Extend current database to larger aspect ratio nozzles
– Acquired data with 16:1 nozzle
2. Verify / connect current small-scale database to larger-scale
rectangular nozzles near surfaces
– Trends with and without surfaces appear to follow from previous work
3. Acquire data suitable for creating / validating empirical jet-
surface interaction noise models
– Acquired data over a range of surface lengths
4. Investigate the effect of nozzle septa on the jet-mixing and jet-
surface interaction noise sources
– Data acquired with 3 septa configurations
• What’s next?
20
National Aeronautics and Space Administration
www.nasa.gov
Goals for JSI-HAR
1. Extend current database to larger aspect ratio nozzles
2. Verify / connect current small-scale database to larger-scale
rectangular nozzles near surfaces
3. Acquire data suitable for creating / validating empirical jet-
surface interaction noise models
4. Investigate the effect of nozzle septa on the jet-mixing and jet-
surface interaction noise sources
21
National Aeronautics and Space Administration
www.nasa.gov
JSI Source and Effect Modeling
• Empirical models have been developed for round nozzles near
surfaces
• First-order modeling for rectangular nozzles based on these
round nozzle models suggest:
– Scaling distances and frequency on nozzle height
– Adjusting potential core length
• Jet potential core length is nondimensionalizing parameter
– Data were acquired with 16:1 nozzle to estimate potential core length
22
National Aeronautics and Space Administration
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Jet Potential Core Length
• JSI source and shielding effect
models both depend on jet
potential core length (xC)
• Surface length in model is xE/xC
• Jet potential core length is
approximately 7.75” for Ma=0.7,
unheated jet
• Model for round jet would give
xC/De ≈ 5.13
• If rectangular nozzle scales by h
instead of De,
xC/h ≈ 5.13 -> xC ≈ 7.7”
23
P0
(lbf/
in2)
Position (in)
Ma=0.7, Unheated
17.5
18
18.5
19
19.5
20
20.5
-20 -15 -10 -5 0
National Aeronautics and Space Administration
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Jet Potential Core Length
• Modeled prediction with adjusted
scaling parameters for
rectangular nozzles
• Peak frequency shift
• Approximate right peak amplitude
(JSI source driven)
• Spectral shape off at high
frequencies
• More development needed!
24
PS
D (
dB
)
Sth
Ma=0.7, Unheated
Prediction
Data
National Aeronautics and Space Administration
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Summary
• A round-to-rectangular convergent nozzle with aspect ratio 16:1 was
designed for acoustic measurements
– Minimized potential noise sources from: (1) internal flow separation and
(2) shock cells
• 16:1 aspect ratio nozzle fabricated for testing
– Inserts to simulate TeDP concept details (septa) rapid prototyped
• Pressure traverse at nozzle exit shows expected flow profile
• Preliminary analysis of noise data consistent with previous experiments
– JSI noise source prominent at low frequencies
– Shielding at only the highest frequencies
• Test on-going through October
– Baseline (no septa), 2:1 / 7 Septa inserts planned
26
