Pressure and Temperature Sensitive Paints
Tianshu Liu
Western Michigan University, Kalamazoo, MI, USA
Keisuke Asai Tohoku University, Sendai, Japan
John P. Sullivan
Purdue University, West Lafayette, IN, USA
Outline
• Historical Remarks on PSP/TSP
• Intensity-Based Measurement and Uncertainty
Analysis based on PSP System Modeling
• Lifetime-Based Measurement and Uncertainty
• Photogrammetry and Integration with PSP/TSP
• Applications of PSP/TSP
• Foundations of PSP/TSP
• Conclusions
Historical Remarks on PSP
• Oxygen quenching (Kausky & Hirsch 1935)
• Flow visualization (Peterson & Fitzgerald 1980)
• Air pressure (Pervushin & Nevsky 1981,
Gouterman 1990)
• Large wind tunnels (Ardasheva et al. 1985,
McLanchlan et al. 1989,
Morris et al. 1993)
• Lifetime (Bykov et al. 1985, Davies et al. 1995)
Historical Remarks on PSP (continued)
• Rotating machinery (Burns et al. 1995, Liu et al. 1997,
Bencic 1997)
• Cryogenic tunnels (Asai et al. 1997, Upchurch et al. 1998)
• Hypersonic tunnels (Troyanovsky et al. 1993,
Nakakita et al. 2000)
• Low-speed flows (Morris et al. 1997, Brown 2000,
Torgerson et a. 1997, Le Sant 2001)
• Flight tests (McLachlan et al. 1992, Lachendro et al. 1998)
Historical Remarks on TSP
• Thermographic Phosphors for hypersonic flows
(Buck 1988, Merski 1998)
• Polymer-based TSP for low-speed, transonic,
supersonic, and hypersonic flows, cryogenic flow,
rotating blades, flight testing
(Liu et al. 1992, Campbell et al 1992, Asai et al. 1994)
Recent Topics of PSP & TSP
(1) Unsteady PSP & TSP in low-speed, transonic,
supersonic, and hypersonic flows
(3) Integration of PSP & TSP with other image-based
flow diagnostics such as deformation, velocity, and
skin friction measurements
(2) Two-component PSP & TSP and lifetime-based
measurements
(4) Measurements of PSP and TSP in rotating blades
and large production wind tunnels
Moshrov VE, Radchenko VN & Fonov SD
“Luminescent Pressure Sensors in Aerodynamic Experiments”
TsAGI, Moscow, 1997
Bell JH, Schairer ET, Mehta R, Hand L
“Surface Pressure Measurements Using Luminescent Coating”
Annual Review of Fluid Mechanics, Vol. 33, 2001
Gregory J, Asai A, Kamada M, Liu T & Sullivan J
“A Review of Pressure Sensitive Paints in Hypersonic and Unsteady Flows”
Journal of Aerospace Engineering, Vol. 222, Part G, pp. 249-290, 2008
Liu T & Sullivan J
“Pressure and Temperature Sensitive Paints”
Springer, Berlin, 2005
Gregory J, Sakaue H, Liu T & Sullivan J
“Fast Pressure Sensitive Paint for Flow and Acoustic Diagnostics”
Annual Review of Fluid Mechanics, Vol. 46, 2014
Reviews and Books on PSP & TSP
Liu T, Campbell B, Burns S & Sullivan J
“Temperature- and Pressure-Sensitive Paints in Aerodynamics”
Applied Mechanics Reviews, Vol. 50, No. 4, pp. 227-246, 1997
Foundations of PSP
Oxygen Permeation
Oxygen Molecules
Polymer Layer
Incident Light Luminescence
Luminophore Model
LuminescenceIncident Light
Oxygen QuenchingLuminophore
Oxygen Molecules
Model Surface
Porous Material
Surface
Conventional polymer PSP
Porous PSP
Ener
gy
So
Ground
State
Singlet Excited States
Triplet Excited
State
S1
S2
T1
Vibrational
Relaxation
Interstystem
Crossing
Internal
Conversion
Vibrational
Relaxation
Internal
and
External
Conversion
PhosphorescenceFluorescenceAdsorption
Jablonsky Energy-Level Diagram
]S])[Q[kkkk(Idt
]S[d1)s(q)ts(iscicfa
1
11
]T])[Q[kkk(]S[kdt
]T[d1)t(q)st(iscp1)ts(isc
1
0111
Kinetics of Luminescence:
Oxygen Quenching & Stern-Volmer Relation
where
T
TT
TR
E1AA
ref
ref
ref
nrref,polymerpolymer
T
TT
TR
E1BB
ref
ref
ref
Dref,polymerpolymer
nrD EE 1
“Ideal PSP”: )T(Apolymer )T(Bpolymer is independent of T
Conditions:
ref
polymerpolymer
refref
p
p)T(B)T(A
I
I
2
refref
ref
p
p)T(C
p
p)T(B)T(A
I
IAlternative Form:
Calibration Results for Bathophen Ruthenium
Chloride in RTV-110 mixed with Silica Gel particles
Stern-Volmer Plots
P/Pref
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
I ref/I
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
243K
253K
258K
263K
268K
273K
283K
293K
linear fit
Ru-Bath
ref
nr
ref T
1
T
1
R
E
)T(I
)T(Iln
Thermal Quenching & Arrhenius Relation
Arrhenius Plots
(1/T - 1/Tref
)103 (K
-1)
-0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4
ln[I(T
)/I(
Tre
f)]
-3
-2
-1
0
1
EuTTA-dope
Ru(bpy)-Shellac
EuTTA
T (deg. C)
-150 -100 -50 0 50 100 150
I/I re
f
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1 23
4
5
67
8
1.1.1.1.1.1.1.1.1. Temperature dependencies of the luminescence intensity for TSP
formulations: (1) Ru(trpy) in Ethanol/Methanol, (2) Ru(trpy)(phtrpy) in GP-197, (3)
Ru(VH127) in GP-197, (4) Ru(trpy) in DuPont ChromaClear, (5) Ru(trpy)/Zeolite in GP-
197, (6) EuTTA in dope, (7) Ru(bpy) in DuPont ChromaClear, (8) Perylenedicarboximide
in Sucrose Octaacetate. (Tref = -150oC). From Liu et al. (1997b)
Calibration Curves for TSPs
Measurement Systems --- Camera System
Measurement Systems --- Laser Scanning System
LaserPMT
2D Scanner
Laser Beam
Luminescence
Computer
Painted Model
Lock-in Amplifier
Modulator
Flow Chart for PSP/TSP Data Processing
PSP System Modeling & Uncertainty Analysis
Geometry of incident light
and luminescent emission Radiative energy transport in PSP
ΩAMK)(λEq)Tp,(hβdΩθcosIAQ s12λ0λΩ
λsλ 2122
Radiative energy flux collected by a detector:
Camera Output
2101λ2op
2
I KKq)TP,(hβ)M(1F
A
4
πGV
IA/4DπA 2
0
1R 2R
sA
Imaging system
aperture area,
Source area
Image of source area
Generalized Stern-Volmer Equation
B(T)
PA(T)
B(T)
P
)t,V(
)t,(VUP
refrefref
2 x
x
)t,(q
)t,(q
)(c
)c(
)(h
)h(
Π
Π
Π
Π)t(ΔD)(ΔD)t(ΔDU
ref0
0
refrefreff
f
refc
c
q0xt2X
X'
x
x'
x
x'x
where
Camera noise
Model deformation
Temperature
PSP calibration
Temporal variation in luminescence
and illumination
Spectral variability and filter leakage
Error Propagation & Total PSP Uncertainty
2/1
2i
i
M
1i
2iPSP
)var(SΔP/P)(
ζ
ζ
1i
2/1VPi SNσ/)(σ
up
Upper Bounds of Elemental Errors
Variable Index
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
P
i
σ
)(σ up
)t(ΔDt
)(ΔDx x
)t(ΔDq0
V
refV
refcc /ΠΠ
refff /ΠΠ
refh/h
refc/c
ref00 /qq
refP
A
B
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15 Pressure mapping
T
Allowable Upper Bounds for a Ru-Based PSP
Uncertainty Due to Shot Noise
1/2
ref
ref
maxrefpe
min
P
PB(T)A(T)1
P
P
B(T)
A(T)1
)(n
1
P
ΔP)(
P/Pref
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Min
imum
pre
ssure
uncert
ain
ty (
%)
0.20
0.24
0.28
0.32
0.36
0.40
T = 293 K
T = 313 K
T = 333 K
Moved Joukowsky Airfoil
Joukowsky Airfoil
x
PSP Uncertainty on an Airfoil in Subsonic Flows
x/c
0.0 0.2 0.4 0.6 0.8 1.0
Un
cert
ain
ty in P
0.0
0.1
0.2
0.3
0.4
0.5
0.6
M = 0.7
M = 0.5
M = 0.3
M = 0.1
Upper Surface
PSP Uncertainty vs. Maximum Pressure Change
Freestream Mach number
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Re
lative
Err
or
or
Va
ria
tio
n
0.001
0.01
0.1
1
Upper Surface
P/ΔPmaxsurf
awPSPΔP/P)(
0TPSPΔP/P)(
ShotNoisePSPΔP/P)(
The minimum pressure resolution indicates the difficulty for PSP
measurement in low-speed flows
Freestream Mach Number
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
Uncert
ain
ty
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Lift
Pitching Moment
Total PSP Uncertainty in Lift and Moment
This also highlights the difficulty for PSP measurement
in low-speed flows
Summary of PSP Accuracy
Temperature effect is the most dominant error source.
The minimum PSP uncertainty is limited by the
photon shot noise.
The limiting low Mach number is determined by the
shot-noise-limited uncertainty and pressure variation
on a surface.
Lifetime Measurement Techniques
δ(t) ) ( A ) E(t, r r ) τ / t exp( ) ( A ) (t, I r r
PSP
Excitation light luminescence
The Stern-Volmer relation
P K 1 τ
τ 0
ref
ref
P
P ) T ( B ) T ( A
τ
τ or
PSP Response to Excitation
First-order model )t,E(τ/Itd/dI r
du),uE(]τ/)ut(exp[)(t,It
0rr General response
]φ)tsin(ωMH1[τ)(A)(t,I eff rr
1n222
nnnn0
τωn1
)φtωsin(nb)φtωcos(na
2
aτ)(A)(t,I rr
Response to
general periodic
excitation
Response to
sine-wave excitation
t (ra d ia n )
0 2 4 6 8 1 0 1 2
Inte
nsit
y
0 .5
1 .0
1 .5
2 .0
2 .5
3 .0
3 .5
4 .0
E xc ita tio n L ig h t
L u m in e s c e n c e
t (ra d ia n )
0 2 4 6 8 10 12
Inte
nsit
y
0
1
2
3
4
5
E xc ita tion L igh t
Lum inescence
t (ra d ia n )
0 2 4 6 8 10 12
Inte
nsit
y
0 .0
0 .5
1 .0
1 .5
2 .0
2 .5
E xc ita tion L igh t
Lum inescence
PSP responses to three types of excitation
Methodologies of Lifetime Measurement
Pulse Method (time-revolved approach)
δ(t))(A)E(t, rr
)τ/texp()(A)(t,I rr
PSP
)τ/texp(α(t)I ii
or
Gated Intensity Ratio Method
(radian)
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6
I2/I1
0.0
0.4
0.8
1.2
1.6
2.0
2.4
cosine wave
sine wave
square wave
triangle wave
) E(t, r
PSP
) (t, I r
dt ) t ( G ) , t ( I I 2 T
2 2
r
Divider
) τ ( F /I I 1 2
dt ) t ( G ) , t ( I I 1 T
1 1
r
For a square-wave gain function and a sine-wave excitation,
H2)τω(1π
H2)τω(1πtdItdI/II
22
221/2f
0
1/f
1/2f12
P/Pref
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
I2/I1
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Modulation frequency = 200 kHz
100 kHz
50 kHz
5 kHz
25 kHz
Uncertainty of Gated Intensity Ratio Method
Calibration error Detector noise
Data-reduction equation:
Error propagation equation:
K
11
V/V1
V/V1
π
H2
K
τωP
2/1
12
120
2
2
22
V2
1
12
V2
0
02
τ2
2
K2
2
T2 V
)Vvar(S
V
)Vvar(S
τ
)τvar(S
K
)Kvar(S
T
)Tvar(S
P
(P)var210
Temp. effect
Photon-Shot-Noise-Limited Uncertainty
PK
)KP1(])KP1(τω[1
τω2π
}H2])KP1(τω[1{2
V
GB
P
P 32/122
0
2
2
0
2
2/122
0
22/1
1
d
P/Pref
0.0 0.5 1.0 1.5 2.0
(P
/P)(
V1/G
Bdh)1
/2
1
2
3
4
B = 0.5
0.6
0.7
0.8
0.9
B
0.0 0.2 0.4 0.6 0.8 1.0
(P
/P)(
V1/G
Bdh)1
/2
0
5
10
15
P/Pref= 0.2
0.5
1.0
1.5
2.0
Fluorescence Lifetime Imaging Systems
Intensified CCD Camera
Photo
Cathode
Micro
Channel Plate Phosphor ScreenFiber-Optic
Taper CCD
e--
e- e-
ICCD structure
FLIM diagram
)(t,I r (t)G)I(t,r INTT
0INT
dt)t(G)r,t(IT
1I
Image
IntensifierCCD
])θtsin(ωm1[G(t)G DD0 )θφos(c)φcos(m5.01
)θφos(c)φcos(m5.01
)θ(I
)θ(I
1DD
2DD
1D
2D
Internally Gated CCD Camera (Fisher & Linne 1999)
CCD architecture Control logic
) D( π
) D( π t d I t d I /I I
1/2f
0
1/f
1/2f 1 2
Input Signal
) t ( I
dt ) t ( I
Overflow Drain
Substrate
Vertical
Register
Readout
Read Out
Gate
Sensor
TTL trigger
TTL Switch
Off On
On Off
Switch TTL
Off
On On
Off
TTL trigger
t d I or dt I 1/f
1/2f
1/2f
0
PSP Images of Impinging Sonic Jet
Intensity Ratio FLIM
Photogrammetry and Integration with PSP/TSP
Mapping PSP Data from
2D images onto 3D space
Generating a Deformed
Grid for PSP Mapping
Image Registration X
Object Space
Y Z
dy
dx
x p
y p
y
x
Perspective center
Principal point
Perturbed
image point
position
‘True’
image point
position
Image Plane
Object point
.)ZZ(m)YY(m)XX(m
)ZZ(m)YY(m)XX(mc
dyyy
,)ZZ(m)YY(m)XX(m
)ZZ(m)YY(m)XX(mc
dxxx
cn33cn32cn31
cn23cn22cn21
pn
cn33cn32cn31
cn13cn12cn11
pn
Collinearity Equations & Perspective Mapping
)Z,Y,X,,,( ccc
)S/S,P,P,K,K,y,x(c, vh2121ppInterior Orientation:
Exterior Orientation:
(1) Direct Linear Transformation (DLT) (Abdel-Aziz &
Karara 1971)
(2) Optimization Method (Liu 2000)
Camera Calibration:
Applications of PSP
U = 30 m/s
AoA = 5 deg
Low-Speed
Airfoil Flow
(Brown 2000):
Low-Speed 75-deg
Delta-Wing Flow
at 25 m/s & AoA =
32 deg
(Engler et al.
2001): -3
-2.5
-2
-1.5
-1
-0.5
0
0.5
-150 -100 -50 0 50 100 150
y (mm)
Cp
Kp 400
512x512, radius=3
1340x1300, radius=3
-4
0
pressure taps
FAVOR Model in Transonic Flow
(Marvin Sellers, AEDC, 2009)
Facility Aerodynamics Validation
and Operations Research (FAVOR)
model
Pressure Coefficient Distributions on the Upper and Lower
Surfaces of the FAVOR Model at AoA of 10o and Mach 0.8
(Marvin Sellers, AEDC 2009)
0.2 0.4 0.6 0.8
-1.6
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
CP
Station B
x/c
a=0o
a=1o
a=3o
a=5o
0.2 0.4 0.6 0.8
-1.6
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
CP
Station C
x/c
a=0o
a=1o
a=3o
a=5o
Supercritical Wing in Cruising Speed (M = 0.74)
(Mebarki & Le Sant 2001)
Hypersonic and Shock Tunnels (Nakakita et al. 2000)
0.8
0.6
0.4
0.2
0.0
P/P
02 (
P0
2=
8,0
00P
a)
2.52.01.51.00.50.0-0.5
X/Lp
PSP (3runs)
Pressure Transducer (3runs)1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
P/P
02 (
P02=
8,0
00
Pa
)
2.52.01.51.00.50.0-0.5
X/Lp
PSP (3runs)
Pressure Transducer (3runs)
Setup
Cooled CCD camera
Image Intensifier
PSP coating model with BAR
Xenon flash lamp
Shock tubeShock tube
Optical window
Optical fiber
Flash lamp driver
Dichroic Beam Splitter
73.9mm
36.95mm
Moving Shock Impinging to Cylinder Normal to Wall
(Asai et al. 2001)
Pressure Taps
(0.3mm x 16) Removable Strips
50mm
Cryogenic Wind Tunnels (Asai et al. 2001)
T = 100K
M = 0.82
T = 100K
M = 0.75
x/c
0.0 0.2 0.4 0.6 0.8 1.0
p/p
0
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
75% span10,000 rpm
14,500 rpm
16,000 rpm
17,000 rpm
17,800 rpm
increasing rpm
Photomultiplier Tube
Long Pass Filter
Argon-ion Laser
(488 nm)
Inlet Contraction
Compressor RotorVariable inlet Guide Vanes
Computer Controlled
Scanning Mirror
High-Speed Axial Flow Compressor
(Liu et al. 1997, Torgerson et al 1997, 1998)
Obliquely Impinging Sonic Jet (Crafton et al. 1999)
Plenum Internal
diffuser
Air inlet
0.5 cm nozzle
H
Geometric
impingement point
Impingement
distance Impingement
plate
Impingement angle
11
12
13
14
15
16
17
18
19
-5 0 5
-2
0
2
4
6
8
10
12
14
S/D
Y/DPressure [psia]
po/pa 2.71
H/D 3.8
10o
pressure
po/pa 2.71
H/D 3.8
10o
Flight Tests (Lachendro 2000)
=0.31
532nm Nd: Yag laser
scanning from cabin window
Mylar strips coated
with PSP and TSP
=0.55
=0.85
=0.31=0.31
532nm Nd: Yag laser
scanning from cabin window
Mylar strips coated
with PSP and TSP
=0.55
=0.85
=0.31 x/c
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
Cp
-1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
0.2
0.4
0.6
0.8
PSP T=-5C
MHI Flight Test Data
1/4 20 Optical
Breadboard
Gimballed
Mirrors
Polarizing
Optic
532nm, 50mW,
Nd: YAG Laser
E-O
Modulator
Focusing
Lens
Spatial
Aperture
Longpass
Filter
P.M.T
.
Linear
Traverse 6X Beam
Expander/ Focuser
Laser Path
Polarizing
Optic
Applications of TSP
Time (sec)0 1 2 3
q (
kW
/m2
)
0
20
40
60
80
100
120Thermocouple at T3G
Paint
Time (sec)0 1 2 3
q (
kW
/m2
)
0
20
40
60
80
100
120Thermocouple at T7G
Paint
Mach 10 Waverider (Liu et al. 1995)
0
20
40
60
80
100
0 25 50 75 100 125 150
Centerline (mm)
q (
W/c
m2)
Gauges
TSP
Heat Transfer Rate
Mach 9.6 Double-Cone (Hubner et al. 2002 )
Time-dependent intensity images (1 ms interval)
Laminar Boundary Layer on a 7-deg Circular Cone at Mach 6
Liu et al. (2013)
Transition on a 7-deg Circular Cone at Mach 6
Heat flux image given by the 1D inverse method
t = 1.5 s Liu et al. (2010)
Boundary Layer Transition Detection
(Cattafesta et al. 1996) (Burner et al. 1999)
(Asai et al. 1996)
(Popernack et al. 1997)
0 1 2 3 4 5 6 71.0
1.2
1.4
1.6
1.8
2.0
2.2
2.4
2.6
2.8
3.0
Empirical value in quasi- conical-symmetric zone
Present data
Stmax
Str
R/
0 10 20 30 40 50 60 70 801.0
1.5
2.0
Str
St
(degree)
inviscid shock
R = 25 mm
R = 20 mm
R = 15 mmR = 10 mm
wall
Shock/Boundary-Layer Interaction (Liu et al. 1995)
Quasi-Conical Symmetry?
Laser Spot Heating and Heat Transfer Measurements
(Campbell et al. 1998)
Heating Laser (1064 nm)
Excitation Laser (532 nm)
Scanning
Mirror
PMT
Band-Pass
Filter
Glass
VAbsorbing
Layer
Painted Model
V, T
SubstrateInsulating
Layer
L
Heat Loss
(Convection)
Measurement
Location
Heat Loss
(Conduction)
kT
n
h T TS
TSP and
Absorber
Heated Spot
(a)
(b)
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
% S
pa
n
0.6 0.7 0.8 0.9
% Chord
120
110
100
90
80
70
60
50
40
30
20
h (W/m2-°C)
Hot-Film Surface Temperature in Shear Flow
(Liu et al. 1994)
-4 -3 -2 -1 0 1 2 3 4 50.0
0.5
1.0
1.5
(X - XL)/L
(Ts
- T
inf)
/(T
m -
Tin
f)
Z/w = -0.5
Z/w = 0.5
Z/w = 0.0
-2 -1 0 1 2
0.4
0.6
0.8
1.0
1.2
1.4
Experiment
Lumped model
(Ts
- T
inf)
/(T
m -
Tin
f)
Z/w
Conclusions
PSP/TSP can provide a tremendous amount of information
on various aerodynamic flows from subsonic to
supersonic to hypersonic flows, which significantly
enhances our understanding of flow physics.
PSP/TSP are an active interdisciplinary research area that
requires close collaboration among specialists in
aerodynamics, chemistry, photophysics, and imaging
technologies.
