Kegerise, Michael A.

Rufer, Shann J.

NASA Technical Reports Server

National Aeronautics and Space Administration!
www.nasa.gov 
Unsteady Heat-Flux Measurements of 
Second-Mode Instability Waves 
Michael A. Kegerise 
& 
Shann J. Rufer 
 
NASA Langley Research Center 
1 NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 
https://ntrs.nasa.gov/search.jsp?R=20160006911 2019-08-31T02:34:19+00:00Z
National Aeronautics and Space Administration!
www.nasa.gov 
Introduction 
•  Atomic Layer Thermopile (ALTP) sensors 
–  Developed by Tim Roediger (2010 Doctoral Thesis, University of Stuttgart, Germany) 
–  Provides a time-resolved heat-flux measurement 
–  Good spatial resolution: ~1 mm2 
–  Frequency response on the order of 1 MHz 
–  Linear static response over several orders of magnitude (from mW/cm2 to kW/cm2) 
•  Well suited for measurements of unsteady heat transfer in a wide range 
of flow problems 
–  Heat transfer in turbomachinery 
–  Stagnation point heating 
–  Shock-boundary layer interactions 
–  Measurements in short duration supersonic and hypersonic facilities 
–  Laminar-to-turbulent transition 
 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 2 
National Aeronautics and Space Administration!
www.nasa.gov 
Objectives 
•  Gain experience with the ALTP sensors for measurements in 
transitional hypersonic boundary layers 
–  Previous work by Roediger et al (2009), Roediger (2010), and Heitmann et al (2010) 
demonstrated this application in short-duration hypersonic wind tunnels 
–  Demonstrate application in our conventional hypersonic blow-down tunnels 
•  Develop the capability to dynamically calibrate the ALTP sensors 
–  Measurements of the sensor frequency response function 
–  Critical for cross-correlations and cross-spectral analysis with multiple sensors 
•  Measure second-mode instability waves on a flat plate model in a  
Mach 6 freestream flow 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 3 
National Aeronautics and Space Administration!
www.nasa.gov 
Atomic Layer Thermopile (ALTP) Sensors 
•  Sensor area of 1 mm2 
•  Nominal bandwidth of ~1 MHz 
•  Nominal static sensitivity of            
48.0 µV/W/cm2  
•  Signal from ALTP sensor is amplified 
with a miniature amplifier placed 
inside the model 
–  AC coupled signal has a fixed gain of 5000 
and bandwidth from 17 Hz to 1 MHz 
–  DC coupled signal has adjustable gain from 
100 to 800 and a bandwidth of 100 kHz 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 4 
Active Area
7.6 mm
4.8 mm
1 mm
1 mm
Perspective and top 
views at 30X optical 
mag.	

Close-up view of 
sensor active area at 
150X optical mag.	

National Aeronautics and Space Administration!
www.nasa.gov 
Experimental Setup for Dynamic Calibration 
of the ALTP Sensors 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 5 
90R:10T
Beam splitter
Temperature controlled
laser diode mount
(500 mW, 670 nm
laser diode)
Collimating Optics
f = 8 mm aspheric lens
Anamorphic prism
with 3.0 Mag.
~3 mm diameter beam
Elliptic beam
~1.0 mm by 3.0 mm
ALTP Sensor
Photo-diode detector
(reference beam)
Adjustable Iris
90R
10T
Function
Generator
Laser Diode Driver
& Temp Control
Shutter connected
to laser interlock
National Aeronautics and Space Administration!
www.nasa.gov 
Frequency Response Measurement Details 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 6 
ALTP
Sensor
Amplifier
Gain: 5000
BW: 17 Hz-1 MHz
Beam
Splitter
Photo-Diode
Sensor
BW > 500 MHz10T
90R
Radiant Heat-Flux
Input
(from laser diode)
Anti-alias Filter
Fc = 900 kHz
16-bit ADC
2 Ms/sec
e(t)
(Reference Input)
q(t)
(Output)
•  Amplitude modulate radiant heat-flux input with a 
sine wave 
•  Collect time-series data for a range of sine-wave 
frequencies 
•  Calculate the frequency-response function between 
the reference input measured by the photo diode 
and the output of the ALTP sensor amplifier 
H(f) =
Gxy(f)
Gxx(f)
|H(f)|
\H(f)
Magnitude	

Relative Phase	

Fs = 2 MHz
Nsamp = 4⇥ 106
Nfft = 50000
Hanning Window, 50% overlap
 f = 40 Hz
Nblk = 160
Acquisition and Processing Parameters	

National Aeronautics and Space Administration!
www.nasa.gov 
Sample Time Series Data for Dynamic Calibration 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 7 
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5−1
−0.5
0
0.5
1
q
(t
)
(W
/
c
m
2
)
t (ms)
−0.1
−0.05
0
0.05
0.1
e
(t
)
(V
)
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1−1
−0.5
0
0.5
1
q
(t
)
(W
/
c
m
2
)
t (ms)
−0.1
−0.05
0
0.05
0.1
e
(t
)
(V
)
1743 Hz 
78.8 kHz 
Red Curve: Reference Photodiode 
Blue Curve: ALTP Sensor 
National Aeronautics and Space Administration!
www.nasa.gov 
Frequency Response of ALTP Sensors 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 8 
102 103 104 105 106
−6
−4
−2
0
2
f (Hz)
|H
(f
)|
(d
B
re
1
)
 
 
102 103 104 105 106
−150
−100
−50
0
50
f (Hz)
̸
H
(f
)
(◦
)
01−01092013
02−05092013
03−04092013
06−02092013
Black Symbols: Pre-Test Measurements 
Blue Symbols: Post-Test Measurements 
f 3dB = 650± 25 kHz
  3dB =  92.9  ± 3.1 
National Aeronautics and Space Administration!
www.nasa.gov 
Experimental Setup 
•  Facility 
–  Langley Aerothermodynamics Laboratory 
20-Inch Mach 6 Tunnel 
–  Conventional blow-down tunnel 
–  Test Gas: Air 
–  Re Range: 1.6 to 28.5x106/m 
–  Total Temperature: 465 to 520 K 
•  Flat plate model 
–  71.12 cm long by 27.94 cm wide 
–  Sharp leading edge 
–  AOA of zero and -5 degrees 
–  ALTP sensors were mounted in a 
streamwise array along model centerline 
–  16 sensor locations were available from    
x = 21 cm to 63 cm with 2.8 cm spacing 
–  For a given run, 4 ALTP sensors were 
installed 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 9 
16 Sensor Ports along model CL	

4 Installed ALTP Sensors	

National Aeronautics and Space Administration!
www.nasa.gov 
Heat Flux Power Spectral Densities 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 10 
10−1 100 101 102 103
10−10
10−9
10−8
10−7
10−6
10−5
f (kHz)
G
q
q(
f
)
(W
/
c
m
2
)2
/
H
z
 
 
Re × 10−6/m
3.5
5.0
6.8
8.1
9.7
13.3
16.6
10−1 100 101 102 103
10−10
10−9
10−8
10−7
10−6
10−5
f (kHz)
G
q
q(
f
)
(W
/
c
m
2
)2
/
H
z
 
 
x, cm
23.7
26.5
29.3
32.1
34.9
37.7
40.5
43.3
46.1
48.9
51.7
Heat Flux Power Spectral Densities at x = 26.54 cm 
for a range of freestream unit Reynolds numbers and 
an AOA of zero degrees 	

Streamwise evolution of heat flux power spectral 
density at a unit Reynolds number of 5 million/m 
and an AOA of zero degrees	

National Aeronautics and Space Administration!
www.nasa.gov 
Sample Heat Flux Time Series 
•  Heat flux time series at several streamwise 
positions acquired simultaneously during a 
run 
•  Time series were band-pass filtered about 
the most unstable second mode frequency 
(70 to 200 kHz) 
•  Unit Reynolds number of 8 million/m 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 11 
0 0.2 0.4 0.6 0.8 1
−1
0
1
t (ms)
q
(W
/
c
m
2
) x = 21.0 cm
0 0.2 0.4 0.6 0.8 1
−1
0
1
t (ms)
q
(W
/
c
m
2
) x = 23.8 cm
0 0.2 0.4 0.6 0.8 1
−1
0
1
t (ms)
q
(W
/
c
m
2
) x = 26.5 cm
0 0.2 0.4 0.6 0.8 1
−1
0
1
t (ms)
q
(W
/
c
m
2
) x = 29.3 cm
National Aeronautics and Space Administration!
www.nasa.gov 
Second-Mode Wave Parameters 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 12 
0 500 1000 1500 20000.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
R
c
p
/
u
e
 
 
Re × 10−6/m
3.5
5.0
6.8
8.1
9.7
13.3
16.6
0 500 1000 1500 20000
0.5
1
1.5
2
2.5
3
R
λ
/
δ
 
 
Re × 10−6/m
3.5
5.0
6.8
8.1
9.7
13.3
16.6
Measured phase speed for the most 
unstable second-mode disturbances	

Measured wavelength for the most 
unstable second-mode disturbances	

Note: The boundary layer thickness, δ, was 
based on the laminar similarity solution with a 
Sutherland viscosity model	

National Aeronautics and Space Administration!
www.nasa.gov 
Run-to-Run and Sensor-to-Sensor 
Repeatability 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 13 
10−1 100 101 102 103
10−10
10−9
10−8
10−7
10−6
10−5
f (kHz)
G
q
q
(f
)
(W
/
cm
2
)2
/
H
z
 
 
Sensor Number
1
6
1
2
10−1 100 101 102 103
10−10
10−9
10−8
10−7
10−6
10−5
f (kHz)
G
q
q
(f
)
(W
/
cm
2
)2
/
H
z
 
 
Sensor Number
2
2
Heat flux power spectral densities measured 
with different sensors at x = 29.34 cm and a 
unit Reynolds number of 5 million/m	

Heat flux power spectral densities measured 
with the same sensor in two different runs at 
x = 40.51 cm and a unit Reynolds number of 
5 million/m	

Issues with static calibration? Accuracy of static sensitivity?	

How flush is sensor plug with model surface? 	

National Aeronautics and Space Administration!
www.nasa.gov 
Summary 
•  Dynamic calibration via laser-based radiative heating 
–  Frequency response of our ALTP sensors was 650 kHz 
–  Sensor-to-sensor frequency response functions were nearly the same 
–  Pre- and post-test measurements of frequency response functions were essentially the 
same 
•  Measurements of second-mode instability waves on a flat plate model 
in a Mach 6 freestream 
–  Results are in-line with what we expect from theory and previous measurements 
–  Most-amplified second-mode frequency varies inversely with boundary-layer thickness 
–  Phase speed is roughly 90% of the freestream velocity 
–  Instability wavelength is roughly twice the boundary-layer thickness 
•  ALTP sensor measurement repeatability 
–  Run-to-run repeatability for a given sensor is acceptable 
–  Sensor-to-sensor measurements at a given port location show some variability 
–  How accurate is the static calibration? 
–  How stable is the static calibration over time? 
–  How flush is the sensor with the model surface? 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 14 
National Aeronautics and Space Administration!
www.nasa.gov 
Backup Slides 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 15 
National Aeronautics and Space Administration!
www.nasa.gov 
Heat-Flux Statistics 
NATO Working Group on Hypersonic Transition, 26-27 March 2015, Tucson, AZ 16 
0 10 20 30 40 50 60 700
0.5
1
1.5
x (cm)
Q
(W
/
c
m
2
)
 
 
Re × 10−6/m
3.5
5.0
6.8
8.1
9.7
13.3
16.6
0 10 20 30 40 50 60 700
0.2
0.4
0.6
0.8
1
x (cm)
〈 q
2
〉 1
/
2
(W
/
c
m
2
)
 
 
Re × 10−6/m
3.5
5.0
6.8
8.1
9.7
13.3
16.6
Mean Heat Flux	
 Broadband R.M.S. Heat Flux	



Unsteady Heat-Flux Measurements of Second-Mode Instability Waves

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server