short course: advanced flow diagnostic techniques for

Copyright Copyright ©© by Dr. Hui Hu @ Iowa State University. All Rights Reserved!by Dr. Hui Hu @ Iowa State University. All Rights Reserved!

Dr. HDr. Hui Huui Hu

Department of Aerospace EngineeringDepartment of Aerospace EngineeringIowa State University Iowa State University

Ames, Iowa 50011, U.S.AAmes, Iowa 50011, U.S.A

Short CourseShort Course: : Advanced Flow Diagnostic Advanced Flow Diagnostic Techniques for Thermal Fluid StudiesTechniques for Thermal Fluid Studies


Course Course OverviewOverview•• This short course aims to give a comprehensive introduction of tThis short course aims to give a comprehensive introduction of the advanced measurement he advanced measurement

techniques widely used for fluid mechanics, aerodynamics, heat ttechniques widely used for fluid mechanics, aerodynamics, heat transfer and combustion studies. ransfer and combustion studies. •• Demonstration lab experiments will also be incorporated in this Demonstration lab experiments will also be incorporated in this coursecourse..•• Lecture Notes are available at:Lecture Notes are available at: http://www.public.iastate.edu/~huhui/teaching/2010http://www.public.iastate.edu/~huhui/teaching/2010--GECDGECD--shortshort--

course/GECDcourse/GECD--shortshort--course.htmlcourse.html

•• Topics to be covered in this short course:Topics to be covered in this short course:–– Pressure Gauge and Transducers Pressure Gauge and Transducers –– Pressure Sensitive Painting (PSP); Temperature Sensitive PaintinPressure Sensitive Painting (PSP); Temperature Sensitive Painting (TSP)g (TSP)–– Shadowgraph and Shadowgraph and SchlierenSchlieren photographyphotography–– Hot Wire Anemometry (HWA)Hot Wire Anemometry (HWA)–– Laser Doppler Laser Doppler VelocimetryVelocimetry (LDV) and Planar Doppler (LDV) and Planar Doppler VelocimetryVelocimetry (PDV) (PDV) –– Particle Image Particle Image VelocimetryVelocimetry ( classic PIV, Stereo PIV, 3( classic PIV, Stereo PIV, 3--D PIV; Holograph PIV, microD PIV; Holograph PIV, micro--PIV)PIV)–– Laser Induced Fluorescence (LIF) and Planar LIFLaser Induced Fluorescence (LIF) and Planar LIF–– Molecular Tagging Molecular Tagging VelocimetryVelocimetry and Thermometry (MTV&T).and Thermometry (MTV&T).

•• Schedule of the short course:Schedule of the short course:–– 0066--JulyJuly, Tuesday,, Tuesday, 11--4pm at GECD4pm at GECD:: Introductions and fundamentals, PSP/TSPIntroductions and fundamentals, PSP/TSP–– 1313--JulyJuly, Tuesday,, Tuesday, 11--4pm at GECD4pm at GECD:: SchlierenSchlieren and Shadowgraph, HWA, LDV/PDV and Shadowgraph, HWA, LDV/PDV –– 2020--JulyJuly, Tuesday,, Tuesday, 11--4pm at GECD4pm at GECD:: PIV; Stereo PIV and 3PIV; Stereo PIV and 3--D PIVD PIV–– 1010--AugAug, Tuesday,, Tuesday, 11--4pm at GECD4pm at GECD:: LIF, MTV and MTT, QD imagingLIF, MTV and MTT, QD imaging–– 1717--AugAug, Tuesday,, Tuesday, 11--4pm at ISU Lab4pm at ISU Lab: : 5~7 demonstration experiments5~7 demonstration experiments


AFD, CFD and EFDAFD, CFD and EFD

Flow PhysicsFlow Physics

ComputationaComputationallFluid DynamicsFluid Dynamics

(CFD)(CFD)

Analytical FluidAnalytical FluidDynamicsDynamics

((AFD)AFD)

Experimental Fluid Experimental Fluid DynamicDynamics s

(EFD)(EFD)


Basics and Fundamentals about Experiments and InstrumentationsBasics and Fundamentals about Experiments and Instrumentations


Review of Fundamentals about Experiments and InstrumentationsReview of Fundamentals about Experiments and Instrumentations

•• Basic concepts and fundamental principlesBasic concepts and fundamental principles•• Similitude and dimension analysis Similitude and dimension analysis •• Measurement uncertainty analysisMeasurement uncertainty analysis•• Fluid Mechanical apparatus: wind tunnels and Fluid Mechanical apparatus: wind tunnels and

water tunnelswater tunnels


Measurable PropertiesMeasurable Properties

•• Material Properties: Material Properties: (Most of them can be found in handbooks)(Most of them can be found in handbooks)

•• Kinematic Properties: Kinematic Properties: Describes the fluid motion w/o considering the force. Describes the fluid motion w/o considering the force. (Position, V, displacement, acceleration, (Position, V, displacement, acceleration, momentum, volume flow rate, mass flow rate, etc)momentum, volume flow rate, mass flow rate, etc)

•• Dynamic properties: Dynamic properties: Related to applied forces. Related to applied forces. (Pressure, shear stress , Torque)(Pressure, shear stress , Torque)

•• Thermodynamic properties: Thermodynamic properties: Heat and Work. Heat and Work. (T, e, h, S)(T, e, h, S)

D,,volume,specific γμρ ,, m


Descriptions of Flow Motion

tLV

t ΔΔ

=→Δ 0

lim

( ) ( )txVtxU ii ,, 0=

⎪⎪⎪

⎩

⎪⎪⎪

⎨

⎧

⇒∂∂

+∂∂

+∂∂

+∂∂

=

∇•+∂∂

=

⇒=

domainEulerianxUU

xUU

xUU

tU

UUtUa

domainLangragianDtVDa

33

22

11

)(rrrr

rrr

r

rr

⎟⎟⎠

⎞⎜⎜⎝

⎛

∂∂

+∂∂

=j

i

j

iij x

UxU

e21

⎟⎟⎠

⎞⎜⎜⎝

⎛

∂∂

+∂∂

=j

i

j

iij x

UxU

μτ

•• LagrangianLagrangian Method Method Focused on fluid particlesFocused on fluid particles

•• EulerianEulerian Method: Method: Focused on space location.Focused on space location.

Acceleration: Acceleration:

Rate of Strain:Rate of Strain:

Shear stress:Shear stress:


Primary Properties and Secondary propertiesPrimary Properties and Secondary properties

•• Primary Properties:Primary Properties: Properties which are independent to each other Properties which are independent to each other

•• Secondary Properties:Secondary Properties: Related to other properties through their definition or Related to other properties through their definition or basic principles basic principles

SrSrStoradianStoradianSolid AngleSolid Angle

radradRadiusRadiusPlane AnglePlane Angle

CdCdCandelaCandelaLuminous intensityLuminous intensity

molmolmolemoleAmount of substanceAmount of substance

AAIIElectric currentElectric current

KKTTTemperatureTemperature

ssttTimeTime

kgkgmmMassMass

MMLLLengthLength

UnitUnitAbbreviationsAbbreviationsNameName


Similitude and Dimensional AnalysisSimilitude and Dimensional Analysis

• Similitude: • The study of predicting prototype conditions

from model observations.

F-22 Raptor Air Superiority Fighter


Similitude and Dimensional AnalysisSimilitude and Dimensional Analysis

),,,( VDfpl μρ=Δ

)(2 μρ

ρVD

Vp

Φ=Δ


Buckingham Buckingham ππ -- TheoremTheorem

•• Step 1: Step 1: List all the variables that are involved in the problem.List all the variables that are involved in the problem.•• Step 2: Step 2: Express each of the variables in terms of basic dimensions.Express each of the variables in terms of basic dimensions.

–– Basic dimension: M, L,T, F Basic dimension: M, L,T, F –– Force Force -- F=MLTF=MLT--22, density , density -- ρρ =ML=ML--33; or ; or ρρ =FL=FL--33TT2.2.

•• Step 3: Step 3: Determine the required number of piDetermine the required number of pi--terms.terms.–– Number of piNumber of pi--terms is equal to terms is equal to kk--rr, where k is the number of , where k is the number of vearibelvearibel in in

the problem, r is the number if reference dimensions required tothe problem, r is the number if reference dimensions required to described described the variables.the variables.

•• Step 4: Step 4: Select a number of repeating variables, where the number requireSelect a number of repeating variables, where the number required is equal to d is equal to the number of reference dimensions.the number of reference dimensions.

•• Step 5;Step 5; Form a piForm a pi--term by multiplying one of the nonterm by multiplying one of the non--repeating variables by the repeating variables by the product of repeating variables, each raised to an exponent that product of repeating variables, each raised to an exponent that will make the will make the combination dimensionless.combination dimensionless.

•• Step 6:Step 6: Repeat Step 5 for each of the remaining nonRepeat Step 5 for each of the remaining non--repeating variables.repeating variables.•• Step 7:Step 7: Check all the resulting pi terms to make sure they are dimensionCheck all the resulting pi terms to make sure they are dimensionlessless•• Step 8:Step 8: Express the final form as a relationship among the piExpress the final form as a relationship among the pi--terms, and think about terms, and think about

what it means.what it means.

),( ,321 rk−ΠΠΠΦ=Π K


Buckingham Buckingham ππ -- TheoremTheorem

•• Example Example

neededistermsrK −⇒== π23;5TFL

LTVTFL

LDFLpl

2

1

24

3

−

−

−

−

=

=

=

==Δ

μ

ρ),,,( VDfpl μρ=Δ

cbal VDp ρΔ=Π1

cbaVD ρμ=Π2

210002413

12

1

02043

01)()())((

VDp

cba

cbcba

cLTFTFLLTLFL lcba

ρΔ

=Π⇒⎪⎩

⎪⎨

⎧

−=−==

⇒⎪⎩

⎪⎨

⎧

=+−=−++−

=+⇒=−−−

VDcba

cbcba

cLTFTFLLTLTFL cba

ρμ

=Π⇒⎪⎩

⎪⎨

⎧

−=−=−=

⇒⎪⎩

⎪⎨

⎧

=+−=−++−

=+⇒=−−−

20002412

111

021042

01)()())((


Commonly used dimensionless parametersCommonly used dimensionless parameters

L

force tensionsurface force inertialWe Number, Weber

force inertialforce lcentrifugaStr Number, Strohal

forcegravity force inertial FrNumber,Froude

massmomentum:Number Schmidt

diffusion heatdiffusion momentum:Number Prandtl

force inertialLift:tCoefficien Lift

force inertialDrag:tCoefficienDrag

force inertialforcepressure Eu number, Euler

force viscousforce inertialRe number, Reynolds

forcelity compressibforce inertialM Number, Mach

∝=

∝=

∝=

==

==

==

==

∝Δ

=

∝=

∝=

σρ

ϖ

γ

γ

ρ

ρ

ρ

μρ

lVVl

V

USc

V

V

LC

V

DC

V

p

VLcV

c

L

D

2

2

2

2

lg

Pr

21

21

21


SimilitudeSimilitude

• Geometric similarity: the model have the same shape as the prototype:

F-16 F-22


Similitude

•• Kinematic similarity: condition where the Kinematic similarity: condition where the velcoityvelcoity ratio is a constant between ratio is a constant between all corresponding points in the flow field. all corresponding points in the flow field. –– The streamline pattern around the model is the same as that arouThe streamline pattern around the model is the same as that around the nd the

prototypeprototype


SimilitudeSimilitude

• Dynamic similarity: Forces which act on corresponding masses in the model flow and prototype flow are in the same ratio through out the entire flow.

pmpg

pI

mg

mI

pg

mg

pI

mI

pmp

pI

m

mI

p

m

pI

mI

pmpp

pI

mp

mI

pp

mp

pI

mI

pg

mg

p

m

pp

mp

pI

mI

FrFrFF

FF

FF

FF

FF

FF

FF

FF

EuEuFF

FF

FF

FF

FF

FF

FF

FF

=⇒=⇒=⇒

=⇒=⇒=⇒

=⇒=⇒=⇒

====

)()(

)()(

)()(

)()(

ReRe)()(

)()(

)()(

)()(

)()(

)()(

)()(

)()(

constant)()(

)()(

)()(

)()(

μμμ

μ

μ

μ


Wind Tunnels and Water TunnelsWind Tunnels and Water Tunnels

• Producing the desired flow field with controlled conditions


Types of Wind TunnelsTypes of Wind Tunnels

Based on Flow Speed:Based on Flow Speed:•• Subsonic or low speed wind tunnels (M<<1.0)Subsonic or low speed wind tunnels (M<<1.0)•• Transonic wind tunnels (MTransonic wind tunnels (M≈≈1.0)1.0)•• Supersonic wing tunnels (1.0 <M<5.0)Supersonic wing tunnels (1.0 <M<5.0)•• Hypersonic wind tunnels (M>5.0) Hypersonic wind tunnels (M>5.0)

Based on Shape:• Open circuit wind tunnel: • Closed circuit wind tunnel:

Other special wind tunnels:• Icing wind tunnel• Tornado simulators • …


Open Circuit Wind Tunnel

•• Suction wind tunnel:Suction wind tunnel: With the inlet open to atmosphere, axial fan or With the inlet open to atmosphere, axial fan or centrifugal blower is installed after test section. centrifugal blower is installed after test section.

•• Blow down wind tunnel:Blow down wind tunnel: A blower is installed at the inlet of wind tunnel A blower is installed at the inlet of wind tunnel which throws the air into wind tunnel. which throws the air into wind tunnel.


Closed circuit wind tunnelClosed circuit wind tunnel


Components of a Wind TunnelComponents of a Wind Tunnel•• Test section Test section •• Contraction sectionContraction section•• Diffuser sectionDiffuser section•• Setting chamberSetting chamber•• Screens and similar structuresScreens and similar structures•• Cooling system / radiatorsCooling system / radiators•• Motors /fans Motors /fans


Function of Contraction

A1

V1

ΔV1ΔV2

V2

A2

10%

2

11 A

Ac = 001.0100

1.01

1

12

2

2 ==Δ

=Δ

VV

cVV

1.01

1 =ΔVVif


Water TunnelsWater Tunnels


Towing TankTowing Tank


Measurement UncertaintiesMeasurement Uncertainties

•• ““AccuracyAccuracy”” is generally used to indicate the relative closeness of agreemeis generally used to indicate the relative closeness of agreement between nt between an experimentallyan experimentally--determined value of a quantity and its true value. determined value of a quantity and its true value.

•• ““ErrorError”” is the difference between the experimentallyis the difference between the experimentally--determined value and its true determined value and its true value; therefore, as error decreases, accuracy is said to increavalue; therefore, as error decreases, accuracy is said to increase. se.

•• Since the true value is not known, it is necessary to estimate eSince the true value is not known, it is necessary to estimate error, and that estimate rror, and that estimate is called an uncertainty, U. is called an uncertainty, U.

•• Uncertainty estimates are made at some confidence levelUncertainty estimates are made at some confidence level——a 95% confidence a 95% confidence estimate, for example, means that the true value of the quantityestimate, for example, means that the true value of the quantity is expected to be is expected to be within the within the ±±U interval about the experimentallyU interval about the experimentally--determined value 95 times out of 100.determined value 95 times out of 100.

truemtruemeasurederror AAEAAA −=⇒−=

smVsmVsmVsmV

t

t

/5error t Measuremen,/100/1error t Measuremen,/10

t?measuremen accurate more is CaseWhich

=Δ==Δ= true

errorrelative A

AE =



•• Total error, Total error, UU, can be considered to be composed of two components:, can be considered to be composed of two components:

–– a random (precision) component, a random (precision) component,

–– a systematic (bias) component,a systematic (bias) component,

–– We usually donWe usually don’’t know these exactly, so we estimate them with t know these exactly, so we estimate them with PP and and BB, respectively., respectively.

•• Precision Error: Random errorPrecision Error: Random error–– Normal Distribution or Gaussian DistributionNormal Distribution or Gaussian Distribution

•• Bias Error: Fixed Error, System ErrorBias Error: Fixed Error, System Error–– Constant Throughout the experimentConstant Throughout the experiment–– Can be positive or NegativeCan be positive or Negative

222 PBU +=X

True valueX=100

Bias errorBias error

precision errorprecision error

measured valueX=101



•• Precise but biasedPrecise but biased•• Unbiased but ImpreciseUnbiased but Imprecise•• Biased and ImpreciseBiased and Imprecise•• Precise and Unbiased Precise and Unbiased

222 PBE +=Qualification of measurement error:Qualification of measurement error:


Repeatability Repeatability and and ReproducibilityReproducibility

Both Bias and Precision ErrorsBoth Bias and Precision ErrorsReproducibilityReproducibility

Precision ErrorPrecision ErrorRepeatabilityRepeatability

• Repeatability is the variability of the measurements obtained by one person while measuring the same item repeatedly. This is also known as the inherent precision of the measurement equipment.

• Consider the probability density functions shown in Figure 1. The density functions were constructed from measurements of the thickness of a piece of metal with Gage A and Gage B. The density functions demonstrate that Gage B is more repeatable than Gage A.

• Reproducibility is the variability of the measurement system caused by differences in operator behavior. Mathematically, it is the variability of the average values obtained by several operators while measuring the same item.

• Figure 2 displays the probability density functions of the measurements for three operators. The variability of the individual operators are the same, but because each operator has a different bias, the total variability of the measurement system is higher when three operators are used than when one operator is used.

ReproducibilityReproducibility

Repeatability



•• We almost always are dealing with a data reduction equation to gWe almost always are dealing with a data reduction equation to get to our et to our final results. final results.

–– In this case, we must not only deal with uncertainty in the measIn this case, we must not only deal with uncertainty in the measured values but ured values but uncertainty in the final results.uncertainty in the final results.

•• A general form looks like this:A general form looks like this:

–– R is the result determined from J independent variables.R is the result determined from J independent variables.

( )JXXXXRR ,,,, 321 K=


Example

ρρ

ρ

pppV

BernoulliVpp

statictotal

statictotal

Δ=

−=

+=

2)(2

)(,21 2

222RRR PBU +=

Uncertainty in velocity V:Uncertainty in velocity V:

∑∑==

⎥⎦

⎤⎢⎣

⎡∂∂

=⎥⎦

⎤⎢⎣

⎡∂∂

=J

ii

iR

J

ii

iR P

XRPB

XRB

1

22

1

22 ;

∑=

=M

jii j

BB1

2

For a large number of samples (N>10) ii SP 2=

( )[ ] ( ) ⎥⎦

⎤⎢⎣

⎡=⎥

⎦

⎤⎢⎣

⎡−

−= ∑∑

==

N

kkii

N

kikii X

NXXX

NS

1

21

1

2 1;1

1


TTechnical Basis for Optical Instrumentationechnical Basis for Optical Instrumentation


The nature of lightThe nature of light

•• According to classical electromagnetic theory, light is considerAccording to classical electromagnetic theory, light is considered to be ed to be radiation that propagates through vacuum in free spaced in the fradiation that propagates through vacuum in free spaced in the form of orm of electromagnetic waves, both oscillating transversely to the direelectromagnetic waves, both oscillating transversely to the direction of wave ction of wave propagation and normal to each other.propagation and normal to each other.

)(2sin),(

)(2sin),(

0

0

TtxBtxBTtxEtxE

zZ

yy

−=

−=

λπ

λπ

λλ : : is wavelengthis wavelengthT :T : is the period of the oscillationis the period of the oscillation

νν: : The reciprocal of the period, is called frequency, The reciprocal of the period, is called frequency, νν =1/T=1/T


The nature of lightThe nature of light--11

•• Light propagation velocity, V= f Light propagation velocity, V= f λλ•• Light propagation velocity in Vacuum, C Light propagation velocity in Vacuum, C = 2.998= 2.998××10108 8 m/sm/s•• Wave front: the locus of all points along the different paths thWave front: the locus of all points along the different paths that have the same at have the same

phase.phase.•• If all the wave fronts are plane, then, the light is considered If all the wave fronts are plane, then, the light is considered to be a plane wave.to be a plane wave.•• If all the wave fronts are spherical or cylindrical, then, the lIf all the wave fronts are spherical or cylindrical, then, the light is considered to be a ight is considered to be a

spherical or cylindrical wave.spherical or cylindrical wave.•• Light propagation is associated with electric and magnetic fieldLight propagation is associated with electric and magnetic fields. They are in phase s. They are in phase

and their amplitudes are related as:and their amplitudes are related as:

•• It is usually sufficiently to analyze electromagnetic waves by cIt is usually sufficiently to analyze electromagnetic waves by considering only onsidering only electric field.electric field.

•• The polarization is associate with the orientation of the plane The polarization is associate with the orientation of the plane of the plane of of the plane of oscillation of the electric field.oscillation of the electric field.

•• Concepts of linearly polarized light, elliptically polarized ligConcepts of linearly polarized light, elliptically polarized light and circularly ht and circularly polarized light, polarized light, unpolarizedunpolarized or randomly polarized light.or randomly polarized light.

00 zy cBE =


The nature of light The nature of light --22

10101414 nm < nm < λλ < 10< 101717 nmnmElectrical power wavesElectrical power waves101088 nm < nm < λλ < 10< 101313 nmnmRadio and TelevisionRadio and Television101077 nm < nm < λλ < 10< 1099 nmnmRadarRadar101066 nm < nm < λλ < 10< 1099 nmnmMicrowavesMicrowaves750 nm < 750 nm < λλ < 10< 1077 nmnmSpace heatingSpace heating380 nm < 380 nm < λλ < 750 nm< 750 nmVisible lightVisible light10 nm < 10 nm < λλ < 380 nm< 380 nmDisinfecting radiationDisinfecting radiation1010--22 nm < nm < λλ < 10< 1022 nmnmXX--raysrays1010--44 nm < nm < λλ < 10< 10--11 nmnmGamma raysGamma raysλλ < 10< 10--44 nmnmCosmic raysCosmic rays

WAVELENGTH WAVELENGTH RANGERANGE

RADIATION TYPERADIATION TYPE


The nature of light The nature of light --22

•• The colors: visible light consists of radiation with wavelength The colors: visible light consists of radiation with wavelength in the range of in the range of 380~750nm (1nm=10380~750nm (1nm=10--99m) which corresponds to the frequency range between 4.0 m) which corresponds to the frequency range between 4.0 ××10 10 15 15 to 7.9 to 7.9 ××10 10 1515 Hz.Hz.

750 nm < 750 nm < λλ < 1000 nm< 1000 nminfraredinfrared647 nm < 647 nm < λλ < 750 nm< 750 nmRed Red 585 nm < 585 nm < λλ < 647 nm< 647 nmOrangeOrange575 nm < 575 nm < λλ < 585 nm< 585 nmYellow Yellow 491 nm < 491 nm < λλ < 575 nm< 575 nmGreenGreen424 nm < 424 nm < λλ < 491 nm< 491 nmBlueBlue380 nm < 380 nm < λλ < 424 nm< 424 nmViolet Violet 0.85 nm < 0.85 nm < λλ < 380 nm< 380 nmUltraviolet (UV)Ultraviolet (UV)

WAVELENGTH WAVELENGTH RANGERANGE

COLORCOLOR


The nature of light The nature of light –– as photonsas photons–– Photon scattering.Photon scattering.

•• one finds experimentally that the frequency of the scattered wavone finds experimentally that the frequency of the scattered wave is changed, e is changed, which does not come out of a wave picture of light. However, whewhich does not come out of a wave picture of light. However, when the light is n the light is viewed as a photon with energy proportional to the associated liviewed as a photon with energy proportional to the associated light wave, ght wave, excellent agreement with experiment is found. excellent agreement with experiment is found.

–– The photoelectric effect: The photoelectric effect: •• When light is shone at a metal plate, it is found that electronsWhen light is shone at a metal plate, it is found that electrons are ejected. are ejected.

These electrons then get accelerated to a nearby plate by an extThese electrons then get accelerated to a nearby plate by an external potential ernal potential difference, and a photoelectric current is established, as belowdifference, and a photoelectric current is established, as below

•• The photons hit an electron in the metal, giving up its energy, The photons hit an electron in the metal, giving up its energy, This is enough This is enough to free the electron from the attractive forces holding it in thto free the electron from the attractive forces holding it in the metal, and it is e metal, and it is accelerated towards the other side, causing a flow of charges anaccelerated towards the other side, causing a flow of charges and hence a d hence a current.current.

•• It is found experimentally that the photoelectric current dependIt is found experimentally that the photoelectric current depends critically on s critically on the frequency of the light being used. This is a feature of the the frequency of the light being used. This is a feature of the energy that the energy that the electrons gain when struck by the light, but in the wave pictureelectrons gain when struck by the light, but in the wave picture the energy of the energy of the light depends on the amplitude, and not on the frequency. the light depends on the amplitude, and not on the frequency.

•• However, in the photon picture of light the energy of the photonHowever, in the photon picture of light the energy of the photon is is proportional to the frequency of the associated wave, which therproportional to the frequency of the associated wave, which therefore provides efore provides a natural explanation of the frequency dependence of the photoela natural explanation of the frequency dependence of the photoelectric ectric current.current.

•• The explanation, which was first given by Einstein and which wonThe explanation, which was first given by Einstein and which won him the him the Nobel Prize.Nobel Prize.

JsconstPlanckh

3410624.6 −×== νε


Light propagate through mediaLight propagate through media

•• Refractive index:Refractive index:

•• Index of refraction of a material generally increasing slightly Index of refraction of a material generally increasing slightly with decreasing with decreasing wavelength of the light. Such phenomena is called wavelength of the light. Such phenomena is called dispersion.dispersion.

1/ 0 >==λλvcn

ρρ

L

L

KKn

−+

=1

21

2.422.42DiamondDiamond

1.921.92zirconzircon

1.771.77sapphiresapphire589nm589nm

1.591.59PolystyrenePolystyrene

1.581.58LexanLexan

1.511.51PlexiglasPlexiglas

1.57~1.891.57~1.89Flint glassFlint glass1.5011.501BenzeneBenzene1.000131.00013HH22

1.521.52Crown glassCrown glass1.4721.472TurpentineTurpentine1.000451.00045COCO22

1.471.47Pyrex glassPyrex glass1.3611.361Ethyl alcoholEthyl alcohol1.000361.00036HeHe

1.461.46Fused quartzFused quartz1.3331.333WaterWater1.000291.00029AirAir

nnSolidSolidnnLiquidLiquidnnGasGas



•• Refraction: Refraction: –– When light propagates through a homogenous medium, its path woulWhen light propagates through a homogenous medium, its path would be d be

straight, whereas, if the medium is nonstraight, whereas, if the medium is non--homogeneous or if the light across from homogeneous or if the light across from one medium to another, the path may change direction gradually oone medium to another, the path may change direction gradually or abruptly. r abruptly. The change of light propagation direction is called refraction.The change of light propagation direction is called refraction.

–– Optically denser medium (n1<n2)Optically denser medium (n1<n2)

1

2

2

1

sinsin

nn

=ϕϕ



•• Total refraction Total refraction

•• reflection reflection

)/(sin2/

sinsin

121

1max2

1221

1

2

2

1

nnnn

nn

cri−=⇒>

>⇒>

=

ϕπϕϕϕ

ϕϕ



•• Optical lens Optical lens Convex lensConvex lens

Concave lensConcave lens



1/ 0 >==λλvcn


AbsorptionAbsorption

•• Light is transmitted through a material, it will be Light is transmitted through a material, it will be absorbed by the molecules of the materialabsorbed by the molecules of the material

•• BeerBeer’’s law:s law:

–– αα iis the absorption or attenuation coefficients the absorption or attenuation coefficient

–– LcLc=1/=1/αα is called penetration depth.is called penetration depth.

–– When L=When L=LLcc, I/I, I/I00=1/e=37%, i.e., 63% energy =1/e=37%, i.e., 63% energy was absorbedwas absorbed

–– Metals have very small Metals have very small LcLc=1/=1/αα..

–– Copper, Copper, LcLc=0.6nm for 100 nm UV light=0.6nm for 100 nm UV light

–– Copper, Copper, LcLc=6.0nm for 1000 nm infrared light.=6.0nm for 1000 nm infrared light.

–– 2nm copper plate as the high pass filter.2nm copper plate as the high pass filter.

)exp(0 LII α−=

LL

I0


illuminationillumination

•• Light sourceLight source–– Thermal source: Thermal source:

•• Lamps: Continuous wave (CW)Lamps: Continuous wave (CW)

–– Laser sourcesLaser sources•• Continuous wave (CW)Continuous wave (CW)•• Pulsed laserPulsed laser•• Singe wavelengthSinge wavelength

–– Point source:Point source:

–– Plane source:Plane source:


Light sourceLight source

–– Thermal light source: Thermal light source: •• Emit electromagnetic radiation as a result of being Emit electromagnetic radiation as a result of being

heated to highheated to high--temperaturetemperature

•• Line sources:Line sources:

•• Continuum sources:Continuum sources:–– Incandescent lamps: heated tungsten filament in a Incandescent lamps: heated tungsten filament in a

evacuated glass container.evacuated glass container.–– Electric discharge lamps: fluorescent lamps. Filled with Electric discharge lamps: fluorescent lamps. Filled with

mercury vapor at low pressure and utilize an electric mercury vapor at low pressure and utilize an electric discharge through it to produce light in ultraviolet (UV) discharge through it to produce light in ultraviolet (UV) range. Through fluorescent, it is convert to visible light.range. Through fluorescent, it is convert to visible light.

–– Flash lamps: tubes containing a noble gas such xenon, Flash lamps: tubes containing a noble gas such xenon, krypton or argon. For their operation, high voltage stored krypton or argon. For their operation, high voltage stored in a capacitor is discharged through the gas, producing a in a capacitor is discharged through the gas, producing a highly luminous corona discharge. Light pulse is about highly luminous corona discharge. Light pulse is about 11μμs or 1 ms.s or 1 ms.

–– Sparks: produced by the electric breakdown of a gas Sparks: produced by the electric breakdown of a gas (helium, neo, argon or air) during an electric discharge (helium, neo, argon or air) during an electric discharge between electrodes. The choice of different electrodes between electrodes. The choice of different electrodes produces sparks of different shapes.produces sparks of different shapes.


LaserLaser

–– Laser: Light Amplification by Stimulated Emission of Laser: Light Amplification by Stimulated Emission of Radiation (LASER)Radiation (LASER)

–– Advantages of laser light over thermal light source: Advantages of laser light over thermal light source:

•• Coherent light (with all light wave front in phase)Coherent light (with all light wave front in phase)

•• Collimated and concentrated (parallel light with Collimated and concentrated (parallel light with small cross area)small cross area)

•• Monochromic (energy concentrated in a very Monochromic (energy concentrated in a very narrow wavelength band)narrow wavelength band)

–– How a laser works:How a laser works:

•• Radiation energy is produced by an activated Radiation energy is produced by an activated medium( can be gas, crystal or semiconductor or medium( can be gas, crystal or semiconductor or liquid solution). liquid solution).

•• The medium consists of particles (atom, ions or The medium consists of particles (atom, ions or molecules).molecules).

•• When a photo, having energy When a photo, having energy hvhv, approaching the , approaching the particles, the photo may be absorbed cause an particles, the photo may be absorbed cause an electron or atoms to be raised temporarily to electron or atoms to be raised temporarily to highhigh--energy level.energy level.

•• When the excited electron or molecule to return When the excited electron or molecule to return ground level, ground level, spontaneous emissionspontaneous emission or or stimulated stimulated emissionemission would take place. would take place.


LaserLaser

–– Spontaneous emissionSpontaneous emission: emit a photo with the : emit a photo with the same energy as that absorbed one, but in same energy as that absorbed one, but in random direction.random direction.

–– Stimulated emission:Stimulated emission: An electron or atom is An electron or atom is already at a higher energy level could become already at a higher energy level could become excited by an incident photo, without absorb excited by an incident photo, without absorb the photo, it will emission another photo with the photo, it will emission another photo with identical energy (frequency), phase, and identical energy (frequency), phase, and direction as the incident photon.direction as the incident photon.

–– External power source is required to maintain External power source is required to maintain the population of the atoms in higher energy the population of the atoms in higher energy level in order to make to stimulated emission level in order to make to stimulated emission taking place continuously.taking place continuously.

–– Optical cavity.Optical cavity.

–– QQ--switchswitch


Commonly used LasersCommonly used Lasers

–– HeliumHelium--neon (Heneon (He--Ne) laserNe) laser

•• Active medium is helium neon atomsActive medium is helium neon atoms

•• Continuous wave laserContinuous wave laser

•• Power 0.3 ~15 Power 0.3 ~15 mWmW

•• λλ =633nm (red)=633nm (red)



–– ArgonArgon--ion (ion (ArAr--ion) laserion) laser

•• Active medium is argon atoms Active medium is argon atoms maintained at the ion state.maintained at the ion state.

•• Continuous wave laserContinuous wave laser

•• Power level: 100 Power level: 100 mWmW ~10 W~10 W

•• Have seven wavelengthsHave seven wavelengths

•• λλ =488nm (blue)=488nm (blue)

•• λλ =514.5nm (green)=514.5nm (green)•• LDV applicationLDV application

•• LIF in liquid flowsLIF in liquid flows



–– NdNd--YAG laserYAG laser

•• SolidSolid--state laserstate laser

•• Active medium: neodymium (NdActive medium: neodymium (Nd+3+3) as active ) as active medium incorporated as an impurity into a medium incorporated as an impurity into a crystal of crystal of YattiumYattium--AluminiumAluminium--GarnetGarnet (YAG) (YAG) as a hostas a host

•• Flash lamp is used as external sourceFlash lamp is used as external source

•• pulsed laser: 10 pulsed laser: 10 --400mJ/pulse or more400mJ/pulse or more

•• Pulse duration: 100ps ~ 10ns Pulse duration: 100ps ~ 10ns

•• WavelenghtWavelenght of tube of tube λλ =1064nm (infrared)=1064nm (infrared)

•• SHG: SHG: λλ =532nm (green), THG: =532nm (green), THG: λλ =355nm =355nm (UV), FHG: (UV), FHG: λλ =266nm (=266nm (deepUVdeepUV))

•• PIV, MTV, PLIFPIV, MTV, PLIF

•• Repetition rate can be as high as 30 Hz.Repetition rate can be as high as 30 Hz.



–– Copper Vapor laserCopper Vapor laser

•• Active medium: copper vaporActive medium: copper vapor

•• Pulsed laser: 10mJ/pulse or morePulsed laser: 10mJ/pulse or more

•• Pulse duration: 15 ~ 60ns Pulse duration: 15 ~ 60ns

•• λλ =510.6nm (green), =510.6nm (green), λλ =578.2nm (yellow) =578.2nm (yellow) •• Repetition rate can be as high as Repetition rate can be as high as

f=5,000~15,000 Hz.f=5,000~15,000 Hz.

•• HighHigh--speed PIV, LIF and othersspeed PIV, LIF and others



–– Dye laserDye laser

•• Active medium: complex multiActive medium: complex multi--atomic atomic organic moleculesorganic molecules

•• λλ =200nm ~ 1500nm=200nm ~ 1500nm

–– ExcimerExcimer laserlaser

•• Gas laser Gas laser KrFKrF and and XeclXecl

•• HighHigh--energyenergy

•• UV wavelengthUV wavelength

•• Pulsed laserPulsed laser

•• high repetition frequencyhigh repetition frequency


Light ScatteringLight Scattering

•• Scattering Scattering –– Scattering is a general physical process whereby Scattering is a general physical process whereby

some forms of radiation, such as light, are forced some forms of radiation, such as light, are forced to deviate from a straight trajectory by one or to deviate from a straight trajectory by one or more localized nonmore localized non--uniformities in the medium uniformities in the medium through which it passes. through which it passes.

•• Elastic Scattering Elastic Scattering –– Excited electron or atoms emits a photo have Excited electron or atoms emits a photo have

exact the same frequency as the incident one.exact the same frequency as the incident one.

•• Inelastic scattering Inelastic scattering –– Excited electron or atoms emits a photo have a Excited electron or atoms emits a photo have a

frequency different from the incident one.frequency different from the incident one.


Elastic scatteringElastic scattering•• Rayleigh Scattering Rayleigh Scattering

–– Light scattering from particles that are smaller than 1/15 of thLight scattering from particles that are smaller than 1/15 of the incident light wavelength (d< e incident light wavelength (d< λλ/15/15).).

–– Efficiency of the scattering from a particle is expressed in terEfficiency of the scattering from a particle is expressed in terms of scattering cross section.ms of scattering cross section.

•• Mie Scattering Mie Scattering –– Light scattering from a particles with its size close on bigger Light scattering from a particles with its size close on bigger than the incident light wavelength than the incident light wavelength

(d > (d > λλ).).–– Conservation of polarization directionConservation of polarization direction–– Angle dependentAngle dependent

•• Forward scattering Forward scattering •• Back scatteringBack scattering

.1065.6

)(

0

229

20

atomtheofwavelengthticcharateristheismT

TR

λσ

λλσσ

−×=

=

. d=1μm b. d=10μm c. d=30μm


Inelastic ScatteringInelastic Scattering•• Raman Scattering Raman Scattering

–– Inelastic scattering from molecules.Inelastic scattering from molecules.–– Chance to occur is about 10Chance to occur is about 10--5 5 s 10s 10--2 2 of times lower than the Rayleigh scatteringof times lower than the Rayleigh scattering–– scattering cross section is several orders smaller than the Raylscattering cross section is several orders smaller than the Rayleigh scatteringeigh scattering–– Stoke transition : the energy of the emitted photo is higher thaStoke transition : the energy of the emitted photo is higher than the absorbed photo. n the absorbed photo. –– AntiAnti--stoke transition: the energy of the emitted photo is lower than stoke transition: the energy of the emitted photo is lower than the absorbed photo.the absorbed photo.–– Time between the absorption and emission: 10Time between the absorption and emission: 10--14 14 s.s.–– antianti--stokes line will be stronger when the temperature is low.stokes line will be stronger when the temperature is low.––


Fluorescence and phosphorescenceFluorescence and phosphorescence

–– Rayleigh and Raman scattering occurs essentially instantaneouslyRayleigh and Raman scattering occurs essentially instantaneously. Not allowing . Not allowing other energy conversion phenomena to occur.other energy conversion phenomena to occur.

–– Fluorescence and phosphorescence: Photoluminescence with time deFluorescence and phosphorescence: Photoluminescence with time delaylay–– FluorescenceFluorescence

•• Emission when the excited from singlet state to ground,Emission when the excited from singlet state to ground,•• lifetime is about 10lifetime is about 10--10 10 ~ 10~ 10--5 5 s. s.

Rhoda mine BRhoda mine B


Fluorescence and phosphorescenceFluorescence and phosphorescence

–– phosphorescencephosphorescence

•• Emission when the excited atom or Emission when the excited atom or molecule from triplet state to ground,molecule from triplet state to ground,

•• lifetime is about 10lifetime is about 10-- 4 4 ~ 10~ 10--5 5 s. s.

0

1000

2000

3000

4000

5000

200 300 400 500 600 700 800

T = 32.0oCT= 25.4 oCT= 19.7 oCT= 14.5 oCT = 10.2oCT= 3 .40 oC

W avelength (nm )

Rel

ativ

e in

tens

ity

Spectraphotom eter O utput vs W ave length

fluorescencefluorescence

PhosphorescencePhosphorescence

MTV chemical: MTV chemical: 11--BrNpBrNp••MMββ--CDCD••ROH complex ROH complex


Light sensing and recordingLight sensing and recording


LensesLenses

•• Focus length: Focus length: •• Depth of focus:Depth of focus:•• ff--numbers or focal ratio : is defined as the ratio of focal numbers or focal ratio : is defined as the ratio of focal

distance of the lens and its clear aperture diameter.distance of the lens and its clear aperture diameter.


Photo detectorPhoto detector

•• Photo detector is a device to convert light to an electric Photo detector is a device to convert light to an electric current through photo electric effect.current through photo electric effect.

•• Quantum efficiency: Quantum efficiency:

•• Noise: Noise: –– Shot noise: due to random fluctuation of the rate Shot noise: due to random fluctuation of the rate

of photon collection and back ground illuminationof photon collection and back ground illumination

–– Thermal noise: caused by amplification of current Thermal noise: caused by amplification of current inside the photo detector and by external inside the photo detector and by external amplifier.amplifier.

•• Dark current: the current produced by the photo Dark current: the current produced by the photo detector even in the absence of a desirable light detector even in the absence of a desirable light source.source.

•• Two kinds of photo detectors: Two kinds of photo detectors: –– Photomultiplier tubes (PMT) Photomultiplier tubes (PMT) –– photodiodes (PD) or photo electric cellsphotodiodes (PD) or photo electric cells

electrons emitted ofNumber :photons absorbed ofNumber :

p

e

p

eq

NN

NN

=η



•• Photomultiplier tubes (PMT) Photomultiplier tubes (PMT) –– Photocathode: absorbs photons Photocathode: absorbs photons

and emits electrons.and emits electrons.–– Dynodes: increase number of Dynodes: increase number of

photonsphotons–– Anodes: outputAnodes: output



•• photodiodes (PD) or photo electric cellsphotodiodes (PD) or photo electric cells–– PP--n junctions of semiconductors, n junctions of semiconductors,

commonly siliconcommonly silicon--silicon type.silicon type.–– High quantum efficiency High quantum efficiency –– But not internal amplification But not internal amplification


Linearity and Dynamic Range of a Digital CameraLinearity and Dynamic Range of a Digital Camera

•• Linearity:Linearity:–– Intensified CCD cameras usually need to Intensified CCD cameras usually need to

check its linearitycheck its linearity

•• Dynamic Range:Dynamic Range:–– The ratio between the fullThe ratio between the full--well capacity well capacity

and the dark current noise.and the dark current noise.–– For example, for a 8For example, for a 8--bit CCD camera, bit CCD camera,

maximum intensity is 2maximum intensity is 288=256, dark =256, dark current noise is about 25, then Dynamic current noise is about 25, then Dynamic range is about 10.range is about 10.

–– Available bits number:Available bits number:•• 8 bit, 16 bit, 24 bit8 bit, 16 bit, 24 bit

0

500

1000

1500

2000

2500

3000

3500

4000

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000 5500 6000

y = a+bx+cx2+dx3

a=1.26, b=1.05, c=-5.36E-5, d=-1.67E-9Gain level 100%Gain level 90%Gain level 80%Gain level 70%y=x

single frame modeexposure time 300usf=2.8

input intensity

outp

ut in

tens

ity

Input Photon Input Photon


Interlaced CamerasInterlaced Cameras

• The fastest response time of human being for images is about ~ 15Hz• Video format:

– PAL (Phase Alternating Line ) format with frame rate of f=25Hz (sometimes in 50Hz). Used by U.K., Germany, Spain, Portugal, Italy, China, India, most of Africa, and the Middle East

– NTSC format: established by National Television Standards Committee (NTSC) with frame rate of f=30Hz. Used by U.S., Canada, Mexico, some parts of Central and South America, Japan, Taiwan, and Korea.

Even fieldEven field(2,4,6(2,4,6……640)640)

Old fieldOld field(1,3,5(1,3,5……639)639)

Even field

Odd field

16.6ms16.6ms

1 frameF=30Hz

480 pixels by 640 pixels480 pixels by 640 pixels

Interlaced cameraInterlaced camera

timetime


Progressive scan cameraProgressive scan camera

•• All image systems produce a clear image of the background All image systems produce a clear image of the background •• Jagged edges from motion with interlaced scan Jagged edges from motion with interlaced scan •• Motion blur caused by the lack of resolution in the 2CIF sample Motion blur caused by the lack of resolution in the 2CIF sample •• Only progressive scan makes it possible to identify the driverOnly progressive scan makes it possible to identify the driver


Mystery of flying rodsMystery of flying rods


Digital cameraDigital camera

•• CCD camera and Intensified CCD (ICCD) camera:CCD camera and Intensified CCD (ICCD) camera:

–– Spatial resolution: 1K by 1k, 4K by 4KSpatial resolution: 1K by 1k, 4K by 4K

–– Frame rate : 30 Hz, High speed camera 1khz ~10K Frame rate : 30 Hz, High speed camera 1khz ~10K hzhz–– In a CCD sensor, every pixel's charge is transferred through a vIn a CCD sensor, every pixel's charge is transferred through a very limited number ery limited number

of output nodes (often just one) to be converted to voltage, bufof output nodes (often just one) to be converted to voltage, buffered, and sent offfered, and sent off--chip as an analog signal. All of the pixel can be devoted to ligchip as an analog signal. All of the pixel can be devoted to light capture, and the ht capture, and the output's uniformity (a key factor in image quality) is high. output's uniformity (a key factor in image quality) is high.

•• CMOS (Complementary metalCMOS (Complementary metal--oxide semiconductor) camerasoxide semiconductor) cameras

–– In a CMOS sensor, each pixel has its own chargeIn a CMOS sensor, each pixel has its own charge--toto--voltage conversion, and the voltage conversion, and the sensor often also includes amplifiers, noisesensor often also includes amplifiers, noise--correction, and digitization circuits, so correction, and digitization circuits, so that the chip outputs digital bitsthat the chip outputs digital bits

–– These other functions increase the design complexity and reduce These other functions increase the design complexity and reduce the area the area available for light capture. With each pixel doing its own conveavailable for light capture. With each pixel doing its own conversion, uniformity is rsion, uniformity is lower. But the chip can be built to require less offlower. But the chip can be built to require less off--chip circuitry for basic operationchip circuitry for basic operation

•• In summary for CMOS camerasIn summary for CMOS cameras

–– Low costLow cost–– Operation versatilityOperation versatility

–– High speedHigh speed

–– Quality is not as high as CCD camerasQuality is not as high as CCD cameras


Pressure Gauge and TransducersPressure Gauge and Transducers


Measurement Techniques for ThermalMeasurement Techniques for Thermal--Fluids StudiesFluids Studies

ThermalThermal--Fluids Fluids measurementmeasurementtechniquestechniques

Intrusive Intrusive techniquestechniques

NonNon--intrusiveintrusivetechniquestechniques

•• PitotPitot probeprobe•• hotwire, hot filmhotwire, hot film•• thermocouplesthermocouples•• etc ...etc ...

•• Laser Doppler Laser Doppler VelocimetryVelocimetry (LDV)(LDV)•• Planar Doppler Planar Doppler VelocimetryVelocimetry (PDV)(PDV)•• Particle Image Particle Image VelocimetryVelocimetry (PIV)(PIV)•• etcetc……

particleparticle--based based techniquestechniques

•• Laser Induced Fluorescence (LIF)Laser Induced Fluorescence (LIF)•• Molecular Tagging Molecular Tagging VelocimetryVelocimetry (MTV)(MTV)•• Molecular Tagging Molecular Tagging TherometryTherometry (MTT)(MTT)•• Pressure Sensitive Paint (PSP)Pressure Sensitive Paint (PSP)•• Temperature Sensitive Paint (TSP)Temperature Sensitive Paint (TSP)•• Quantum Dot ImagingQuantum Dot Imaging•• etc etc ……

moleculemolecule--based based techniquestechniques

Pressure, velocity, temperature, density (concentration), etc..


IntroductionIntroduction

•• Pressure measurements are the primary measurements made in most Pressure measurements are the primary measurements made in most practical aerodynamic testing or basic fluid mechanics experimenpractical aerodynamic testing or basic fluid mechanics experiments.ts.

•• Surface pressure measurements are used for:Surface pressure measurements are used for:•• Identifying specific flow phenomena (boundary layer separation, Identifying specific flow phenomena (boundary layer separation,

shock wave impingement, etc) that are not easily measured by shock wave impingement, etc) that are not easily measured by ““standard pressure tapstandard pressure tap”” measurements.measurements.

•• Validation of computational codesValidation of computational codes•• Loads calculations by integration of the surfaces pressuresLoads calculations by integration of the surfaces pressures


Pressure measurements

• Pressure is defined as the amount of force that presses on a certain area. – The pressure on the surface will increase if you make the force on an area bigger. – Making the area smaller and keeping the force the same also increase the pressure.– Pressure is a scalar

dAdF

AFP nn ==

dA

ndF

τ̂

n̂


Pressure measurements

ambabsolutegauge PPP −=

Manometer


Mechanical Pressure Gauges Mechanical Pressure Gauges --11

Fluid chamberFluid chamber

weightweight

pumppump

cylindercylinderplungerplunger

Calibration Calibration pressurepressure

PP

Deadweight gauges:• High accuracy

• Usually used for the calibration of other instruments

• Application range : 102~108 pa

•Uncertainty is within 0.01% ~0.05% of the reading


Mechanical Pressure Gauges Mechanical Pressure Gauges --22

ElasticElastic--element gauges:element gauges:

•• Contain an elastic elements that deforms under pressure and Contain an elastic elements that deforms under pressure and creates a linear or angular displacementcreates a linear or angular displacement

•• The displacement is either displayed on a dial by means of The displacement is either displayed on a dial by means of purely mechanical linkages or transformed to an electric signal purely mechanical linkages or transformed to an electric signal that can be displayed or recorder at will.that can be displayed or recorder at will.

•• They usually used for monitoring supply pressureThey usually used for monitoring supply pressurep

p

p

Cross sectional shape Curved Bourdon tube

Twisted Bourdon tube


Electrical Pressure transducersElectrical Pressure transducers

•• These devices provides an electric output signal that is These devices provides an electric output signal that is linearly or nonlinearly dependent on the absolute pressure or linearly or nonlinearly dependent on the absolute pressure or a pressure difference.a pressure difference.

•• They can be categorized as:They can be categorized as:–– Molecular transducers: Molecular transducers:

•• Applied pressure or force produces a change (on the Applied pressure or force produces a change (on the molecular level) of a electrical property of material.molecular level) of a electrical property of material.

•• PiezoPiezo--electric material such as quartz crystal: change electric material such as quartz crystal: change in internal dipole moments of the molecules of the in internal dipole moments of the molecules of the crystal when the pressure or force is applied.crystal when the pressure or force is applied.

–– Parametrical transducers:Parametrical transducers:•• The gross electrical parameter (resistance, The gross electrical parameter (resistance,

inductance, capacitance) of an associate electrical inductance, capacitance) of an associate electrical parameter is altered by applied force.parameter is altered by applied force.

•• VariableVariable--capacitance transducercapacitance transducer p

E


Wall Pressure measurements Wall Pressure measurements --11

•• Making small orifice (pressure tap) facing the flow.Making small orifice (pressure tap) facing the flow.

•• Machining small hole could be difficultMachining small hole could be difficult•• d = 0.5~3.0mm in practiced = 0.5~3.0mm in practice•• l/dl/d = 5 ~ 15 is common used= 5 ~ 15 is common used

•• Potential effect on the wall roughnessPotential effect on the wall roughness•• Effects of unsteady shock wave, and shockEffects of unsteady shock wave, and shock--

boundaryboundary--layer interactions for transonic and layer interactions for transonic and supersonic flows:supersonic flows:

•• PSP method to be introduced laterPSP method to be introduced later

V, P

PPmm

ll

dd

0>−=Δ PPp m


Wall Pressure measurements Wall Pressure measurements -- 22

•• For a unsteady flow, the dynamic response of a For a unsteady flow, the dynamic response of a pressure acquisition system is a key issue!pressure acquisition system is a key issue!

–– Dynamic response of the pressure transducersDynamic response of the pressure transducers–– Dynamic response of the connection tubingDynamic response of the connection tubing

•• Remote connectionRemote connection–– Dynamic response is lowDynamic response is low–– Spatial resolution is highSpatial resolution is high

•• Cavity mountingCavity mounting–– Dynamic response is goodDynamic response is good–– Spatial resolution is highSpatial resolution is high

•• Flush mountingFlush mounting–– Dynamic response is highDynamic response is high–– Spatial resolution is lowSpatial resolution is low

Pressure Pressure transducerstransducers

VV

Connection Connection tubingtubing

pressure pressure transducertransducer

VV

VV

pressure pressure transducertransducer


Pressure Measurements inside Flow FieldPressure Measurements inside Flow Field

•• NonNon--intrusive technique is unavailable for direct intrusive technique is unavailable for direct pressure measurementspressure measurements

–– Based on NBased on N--S equation to calculate pressure field using S equation to calculate pressure field using the measured (PIV) velocity field. the measured (PIV) velocity field.

•• Static probe: for static pressure measurementsStatic probe: for static pressure measurements•• PitotPitot probe: for total pressure measurementsprobe: for total pressure measurements•• PitotPitot--static probe: for static and total pressures static probe: for static and total pressures

measurements (velocity measurements)measurements (velocity measurements)•• MultiMulti--hole probe:hole probe:


Pressure Sensitive Paint (PSP) / Pressure Sensitive Paint (PSP) / Temperature Sensitive Paint (TSP)Temperature Sensitive Paint (TSP)


IntroductionIntroduction

Conventional pressure measurements: Transducers or tapsConventional pressure measurements: Transducers or taps•• Discrete preDiscrete pre--determined locationsdetermined locations•• Very high accuracy (< 0.05% FS)Very high accuracy (< 0.05% FS)•• Well understood with long testing backgroundWell understood with long testing background•• High data rate with scanned systems (1000+)High data rate with scanned systems (1000+)•• Limitations to were they can be installedLimitations to were they can be installed•• Potential effect on the flow field Potential effect on the flow field –– intrusive measurementsintrusive measurements•• Expensive installation costsExpensive installation costs

-0.10-0.05

00.050.100.15

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

X/C

Y/C

airfoilairfoil

test sectiontest section

incomingincomingflowflow


Pressure Sensitive Paint (PSP)Pressure Sensitive Paint (PSP)

•• Sprayed over entire exterior surfaceSprayed over entire exterior surface•• nonnon--intrusive pressure measurementsintrusive pressure measurements•• high spatial resolution with resolution limited only by detectiohigh spatial resolution with resolution limited only by detection systemn system•• Limited to optical access applicationsLimited to optical access applications•• Inexpensive application costsInexpensive application costs•• Relatively expensive initial costs to setup the systemRelatively expensive initial costs to setup the system•• HighHigh--speed applicationsspeed applications•• Newer method that is still being fully explored for lowNewer method that is still being fully explored for low--speed applications.speed applications.


Basic Principles of Pressure Sensitive Paint (PSP)Pressure Sensitive Paint (PSP)

•• Composition of Air: 78.08% NComposition of Air: 78.08% N22, 20.95% O, 20.95% O22, 0.93% , 0.93% ArAr, 0.03% CO, 0.03% CO22, 0.002% Ne, plus , 0.002% Ne, plus lesser amounts of Methane, Helium, Krypton, Hydrogen, Xenon.lesser amounts of Methane, Helium, Krypton, Hydrogen, Xenon.

•• The pressure of air can be determined if the particle pressure oThe pressure of air can be determined if the particle pressure of oxygen (i.e. oxygen f oxygen (i.e. oxygen concentration) can be measured. concentration) can be measured.

•• A typical pressure sensitive paint is comprised of two main partA typical pressure sensitive paint is comprised of two main parts: an oxygen sensitive s: an oxygen sensitive fluorescent molecule and an oxygen permeable binderfluorescent molecule and an oxygen permeable binder



•• The pressure sensitive paint method is based on the sensitivity The pressure sensitive paint method is based on the sensitivity of certain luminescent of certain luminescent molecules to the presence of oxygen. molecules to the presence of oxygen.

–– When a luminescent molecule absorbs a photon, it is excited to aWhen a luminescent molecule absorbs a photon, it is excited to an upper singlet energy n upper singlet energy state. The molecule then typically recovers to the ground state state. The molecule then typically recovers to the ground state by the emission of a photon by the emission of a photon of a longer wavelength (i.e. fluorescence or phosphorescence ). of a longer wavelength (i.e. fluorescence or phosphorescence ).

–– In some materials, oxygen can interact with the molecule so thatIn some materials, oxygen can interact with the molecule so that the transition to the the transition to the ground state is ground state is radiationlessradiationless, this process is known as oxygen quenching. , this process is known as oxygen quenching.

–– The rate at which these two processes compete is dependent on thThe rate at which these two processes compete is dependent on the partial pressure of e partial pressure of oxygen present, with a higher oxygen pressure quenching the moleoxygen present, with a higher oxygen pressure quenching the molecule more, thus giving cule more, thus giving off a lower intensity of light.off a lower intensity of light.



•• For oxygen quenching, the intensity decrease can be described byFor oxygen quenching, the intensity decrease can be described by the wellthe well--known known SternStern--VolmerVolmer equation:equation:

•• ττ is the lifetime, I is the intensityis the lifetime, I is the intensity•• KKSVSV is the Sternis the Stern--VolmerVolmer constantconstant•• Q is the quencher or partial pressure of oxygenQ is the quencher or partial pressure of oxygen


Advantages of Pressure Sensitive Paint (PSP)Advantages of Pressure Sensitive Paint (PSP)

•• Pressure sensitive paint has numerous advantages over conventionPressure sensitive paint has numerous advantages over conventional pressure taps and al pressure taps and transducers. transducers.

–– The most obvious is that PSP is a field measurement, allowing foThe most obvious is that PSP is a field measurement, allowing for a surface pressure r a surface pressure determination over the entire model, not just at discrete pointsdetermination over the entire model, not just at discrete points. Hence, PSP provides a much . Hence, PSP provides a much greater spatial resolution than pressure taps, and disturbances greater spatial resolution than pressure taps, and disturbances in the flow are immediately in the flow are immediately observable. observable.

•• PSP also has the advantage of being a nonPSP also has the advantage of being a non--intrusive technique. intrusive technique. –– Use of PSP, for the most part, does not affect the flow around tUse of PSP, for the most part, does not affect the flow around the model, allowing its use he model, allowing its use

over the entire model surface.over the entire model surface.–– The use of PSP eliminates the need for a large number of pressurThe use of PSP eliminates the need for a large number of pressure taps, which leads to more e taps, which leads to more

than one benefit. Since pressure taps do not need to be installethan one benefit. Since pressure taps do not need to be installed, models can be constructed d, models can be constructed in less time, and with less money than before. in less time, and with less money than before.

–– Also, since holes do not need to be drilled in the model for theAlso, since holes do not need to be drilled in the model for the installation of taps, the model installation of taps, the model strength is increased, and higher Reynolds numbers can be obtainstrength is increased, and higher Reynolds numbers can be obtained. ed.

–– Not only does the PSP method reduce the cost of the model constrNot only does the PSP method reduce the cost of the model construction, but it also reduces uction, but it also reduces the cost of the instrumentation needed for data collection. In athe cost of the instrumentation needed for data collection. In addition, the equipment needed ddition, the equipment needed for PSP costs less than pressure taps, but it can also be easilyfor PSP costs less than pressure taps, but it can also be easily reused for numerous models. reused for numerous models.

•• In aircraft design, PSP has the potential to save both time and In aircraft design, PSP has the potential to save both time and money. money. –– The continuous data distribution on the model provided by PSP caThe continuous data distribution on the model provided by PSP can easily be integrated over n easily be integrated over

specific components, which can provide detailed surface loads. specific components, which can provide detailed surface loads. –– Since a model for use with the PSP technique is faster to constrSince a model for use with the PSP technique is faster to construct, this allows for load data uct, this allows for load data

to be known much earlier in the design processto be known much earlier in the design process


Disadvantages of Pressure Sensitive Paint (PSP)Pressure Sensitive Paint (PSP)

•• One of these characteristics is that the response of the luminesOne of these characteristics is that the response of the luminescent molecules in the PSP cent molecules in the PSP coating degrades with time of exposure to the excitation illumincoating degrades with time of exposure to the excitation illumination. ation.

–– This degradation occurs because of a photochemical reaction thatThis degradation occurs because of a photochemical reaction that occurs when the occurs when the molecules are excited. molecules are excited.

–– Eventually, this degradation of the molecules determines the useEventually, this degradation of the molecules determines the useful life of the PSP ful life of the PSP coating. coating.

–– This characteristic becomes more important for larger models, asThis characteristic becomes more important for larger models, as the cost and time of the cost and time of PSP reapplication becomes a significant factor. PSP reapplication becomes a significant factor.

•• A second undesirable characteristic of PSP is that the emission A second undesirable characteristic of PSP is that the emission intensity is affected by the intensity is affected by the local temperature. local temperature.

–– This behavior is due to the effect temperature has on the energyThis behavior is due to the effect temperature has on the energy state of the state of the luminescent molecules, and the oxygen permeability of the binderluminescent molecules, and the oxygen permeability of the binder. .

–– This temperature dependence becomes even more significant in comThis temperature dependence becomes even more significant in compressible flow pressible flow tests, where the recovery temperature over the model surface is tests, where the recovery temperature over the model surface is not uniform.not uniform.


ImplementationImplementation of of Pressure Sensitive Paint (PSP)Pressure Sensitive Paint (PSP)

•• Intensity based Methods (most common)Intensity based Methods (most common)–– FullFull--field using camerafield using camera–– Point systems using scanning laserPoint systems using scanning laser

•• lifetime based Methods (lifetime decay)lifetime based Methods (lifetime decay)–– FullFull--field using camerafield using camera–– Point systems using scanning laserPoint systems using scanning laser

••


Intensity based PSPIntensity based PSP

•• The SternThe Stern--VolmerVolmer equation is rewritten in the equation is rewritten in the popular intensity ratio form:popular intensity ratio form:

•• A and B are highly dependent on the A and B are highly dependent on the luminophoreluminophore and binder material as well as and binder material as well as the temperature sensitivity of the materials the temperature sensitivity of the materials used to make the paint. A 2nd order curve used to make the paint. A 2nd order curve generated from calibration data is most often generated from calibration data is most often used.used.



•• Requires two readings, a reference at Requires two readings, a reference at constant pressure (wind off) and an constant pressure (wind off) and an unknown data point (windunknown data point (wind--on)on)

•• Ratio of intensities IRatio of intensities IREFREF/I is inversely /I is inversely proportional to the air pressureproportional to the air pressure

•• The excitation and detection systems must be The excitation and detection systems must be spectrally separated, (>10spectrally separated, (>10--6 attenuation in 6 attenuation in stop band).stop band).

•• Simplest technique, most sensitive Simplest technique, most sensitive •• Very sensitive to motion between windVery sensitive to motion between wind--off off

and windand wind--onon•• A long period of time can elapse between A long period of time can elapse between

reference and data.reference and data.•• images resulting in significant changes in images resulting in significant changes in

contamination of paint, light stability, etc contamination of paint, light stability, etc that cannot be normalized by the reference that cannot be normalized by the reference condition.condition.



•• Advantages:Advantages:•• Eliminate wind off images and image Eliminate wind off images and image

registration problems. It works in theory registration problems. It works in theory •• In practice, due to homogeneity problems In practice, due to homogeneity problems

of dispersing of two kinds of molecules, it of dispersing of two kinds of molecules, it actually requires a double set of ratios, actually requires a double set of ratios, often called ratio of ratios method.often called ratio of ratios method.


Intensity based PSPIntensity based PSP--temperature compensationtemperature compensation

•• Advantages:Advantages:•• Measure temperature to compensate Measure temperature to compensate

for temperature sensitivity of PSP.for temperature sensitivity of PSP.•• This technique requires all four This technique requires all four

images to be aligned.images to be aligned.


LifetimeLifetime--based PSPbased PSP

•• Easiest to do with a point measurement, but Easiest to do with a point measurement, but can use time resolved cameras to measure can use time resolved cameras to measure lifetime decays of the probe molecules.lifetime decays of the probe molecules.

•• Point measurements require a pulsed light Point measurements require a pulsed light source and detector (PMT, PD)source and detector (PMT, PD)

•• Time resolved imaging requires a double Time resolved imaging requires a double pulse type experiment to measure the decay pulse type experiment to measure the decay times (gated camera, interline transfer times (gated camera, interline transfer camera capable of multiple flash integration).camera capable of multiple flash integration).


LifetimeLifetime--based PSPbased PSP

•• Benefits:Benefits:–– Eliminates the need for aligning two or three Eliminates the need for aligning two or three

images since the pair of (or three ) images are images since the pair of (or three ) images are taken at the same condition relatively close in taken at the same condition relatively close in time (microtime (micro--seconds).seconds).

–– Pressure and temperature distributions can be Pressure and temperature distributions can be determined simultaneously. determined simultaneously.

•• Disadvantages:Disadvantages:–– Requires three gates to generate two equations Requires three gates to generate two equations

of gate ratios to solve for pressure and of gate ratios to solve for pressure and temperature at each point (pixel).temperature at each point (pixel).

–– Camera noise is much higher, especially gated Camera noise is much higher, especially gated intensified cameras.intensified cameras.

–– Paints have tended to be more spatially noisy Paints have tended to be more spatially noisy from lifetime differences between molecules from lifetime differences between molecules (homogeneity problem).(homogeneity problem).


PSP/TSP coatingsPSP/TSP coatings

•• PSP coatings used at NASA GRCPSP coatings used at NASA GRC–– Boeing PF2B Boeing PF2B –– ruthenium ruthenium bathophenanthrolinebathophenanthroline in silicone rubber binder in silicone rubber binder

(soft(soft–– paint, chlorinated solvent)paint, chlorinated solvent)–– UW (ISSI) FIB UW (ISSI) FIB –– PtTFPPPtTFPP in FIB copolymer binder (hard, good steady state in FIB copolymer binder (hard, good steady state

paint)paint)–– NASA Langley NASA Langley –– PtTFPPPtTFPP in FEM (very hard, very smooth finish)in FEM (very hard, very smooth finish)–– ISSI solISSI sol--gel gel –– Ru(ph2Ru(ph2--phen) and phen) and PtTFPPPtTFPP on solon sol--gels (higher frequency gels (higher frequency

response)response)–– Anodized aluminum Anodized aluminum –– dip coated Ru(ph2dip coated Ru(ph2--phen) on anodized surface (very phen) on anodized surface (very

high freq. response)high freq. response)–– UW UW PtOEPPtOEP in MAX acrylic copolymer (ice paint)in MAX acrylic copolymer (ice paint)

•• TSP coatings TSP coatings –– Boeing TSP (range: 0 to 100Boeing TSP (range: 0 to 100°°C, sensitivity ~ C, sensitivity ~ --3%/3%/°°C)C)–– EuTTAEuTTA in commercial clear or shellac (in commercial clear or shellac (--20 to 8020 to 80°°C, ~ C, ~ --4%/4%/°°C)C)–– ThermographicThermographic phosphors in high temp binders (phosphors in high temp binders (--20 to >100020 to >1000°°C)C)


Intensity based PSPIntensity based PSP•• Excitation:Excitation:

–– Continuous Sources: Continuous Sources: LEDsLEDs, Filtered lamps , Filtered lamps (Halogen, Xenon), Lasers(Halogen, Xenon), Lasers

–– Pulsed Sources for instantaneous or periodic Pulsed Sources for instantaneous or periodic measurements: measurements: LEDsLEDs, Xenon, strobes/flash, Xenon, strobes/flash

•• DetectorsDetectors–– Cooled Scientific grade CCD cameras (slow Cooled Scientific grade CCD cameras (slow

scan, low noise), PMT, PDscan, low noise), PMT, PD

Typical PSP absorption and emission spectra Typical PSP absorption and emission spectra [from McLachlan and Bell, 1995][from McLachlan and Bell, 1995]


Calibration for PSPCalibration for PSP•• AA--priori Calibrationspriori Calibrations•• Paints are typically calibrated in a cell that varies pressure aPaints are typically calibrated in a cell that varies pressure and temperature and has a nd temperature and has a

reference measurement reference measurement –– this calibration is used when no onthis calibration is used when no on--model instrumentation model instrumentation exists. exists.

•• InIn--situ Calibrationsitu Calibration–– Uses standard onUses standard on--model instrumentation to calibrate the paint/images in placemodel instrumentation to calibrate the paint/images in place–– Compensates for temperature differences from reference data, spaCompensates for temperature differences from reference data, spatial temperature tial temperature

differences are averaged among all the points used to generate adifferences are averaged among all the points used to generate a calibrationcalibration•• In practice both calibrations are typically usedIn practice both calibrations are typically used


Calibration setupCalibration setup

Heat sinkHeat sink--external flowexternal flow

Silica quartz windowSilica quartz window

Pressure Pressure GuageGuage

DSA ModuleDSA Module

UV LampUV Lamp

Test sample insideTest sample inside

CCDCCDCameraCamera FilterFilter

Pressure controlPressure control

• Pressure air pipe to control the pressure in the chamber• Water recirculation to control the temperature on the

sample plate


PSP calibration image processPSP calibration image process

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

5

1.41.351.31.251.21.151.11.0510.950.90.850.80.750.70.650.60.550.5

IntensityRatio

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

5

120011001000900800700600500400300200100

Intensity

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

5

120011001000900800700600500400300200100

Intensity

X (mm)Y

(mm

)

-10 -5 0 5 10-10

-5

0

5

1.41.351.31.251.21.151.11.0510.950.90.850.80.750.70.650.60.550.5

IntensityRatio

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

5

120011001000900800700600500400300200100

Intensity

X (mm)

Y(m

m)

-10 -5 0 5 10-10

-5

0

5

120011001000900800700600500400300200100

Intensity

Reference Intensity: Iref

Reference Intensity: Iref

P/Pref=7.2: Intensity Intensity ratio: Iref/I

P/Pref=0.23 Intensity Intensity ratio: Iref/I


Calibration curve Calibration curve –– Positive pressurePositive pressure

• Fit function: y=0.00149x^3-0.0510x^2+0.672x+0.436• Error level is below 1%

Calibration curve for the paint positive pressure and error analysis

-0.010

-0.005

0

0.005

0.010

1.0 1.5 2.0 2.5 3.0 3.5

Intensity ratio under different pressureEr

ror %

((I r-I av

e)/Iav

e100%

)

1.0

1.5

2.0

2.5

3.0

3.5

1 2 3 4 5 6 7

y = +0.00149x3 -0.0510x2 +0.672x1 +0.436, max dev:0.0241, r2=1.00

P/Pref

Inte

nsity

Rat

io, I

ref/I


0.6

0.7

0.8

0.9

1.0

0.2 0.4 0.6 0.8 1.0

y = +0.217x3 -0.617x2 +0.946x1 +0.456, max dev:0.00550, r2=1.00

Pressure Ratio P/Prref

Inte

nsity

Rat

io I re

f /I

Calibration curve Calibration curve –– Vacuum pressureVacuum pressure

Calibration curve for the PSP paint under vacuum pressure and error analysis

Fit function: y=0.217x^3-0.617x^2+0.946x+0.456Error level is below 1%

-0.010

-0.005

0

0.005

0.010

0.2 0.4 0.6 0.8 1.0

Pressure ratioEr

orr%

(( Ir- I

r ef)/

I r ef1

00%

)


Uncertainty for PSPUncertainty for PSP•• Characterization of the paint and calibration errors (aCharacterization of the paint and calibration errors (a--priori, inpriori, in--situ calibration, situ calibration,

photo degradation, paint contamination, paint intrusiveness, timphoto degradation, paint contamination, paint intrusiveness, time response)e response)•• Measurement system errors (detector noise, illumination spectralMeasurement system errors (detector noise, illumination spectral and temporal and temporal

stability, spectral leakage)stability, spectral leakage)•• Signal analysis errors (registration from model motion and deforSignal analysis errors (registration from model motion and deformation, mation,

incomplete temperature compensation, self illumination, incomplete temperature compensation, self illumination, resectioningresectioning on a nonon a non--deformed grid)deformed grid)

•• The major contributor is temperature uncertainty which can accouThe major contributor is temperature uncertainty which can account for up to nt for up to 90% of the total uncertainty90% of the total uncertainty


Applications of PSP TechniqueApplications of PSP Technique

PSP combined with PIVPSP combined with PIV

PSP measurement resultPSP measurement result


Application ExamplesApplication Examples


PSP Technique for Low Speed ApplicationsPSP Technique for Low Speed Applications

PSP measurements of PSP measurements of a 2002 Ford Thunderbirda 2002 Ford Thunderbird

VV∞∞=50m/s=50m/s


Applications of PSP TechniqueApplications of PSP Technique

TimeTime--resolved PSP measurements on the front and lateral side surfacesresolved PSP measurements on the front and lateral side surfaces of a 3of a 3--D D square cylinder (square cylinder (YoritaYorita et al. 2010) et al. 2010)

VV∞∞=50m/s=50m/s


Wall Slot Jets Pertinent toWall Slot Jets Pertinent to Trailing Edge Cooling of Turbine BladesTrailing Edge Cooling of Turbine Blades

•• Thermodynamic analysis reveals that Thermodynamic analysis reveals that thermal efficiency and power output thermal efficiency and power output of a gas turbine can be increased of a gas turbine can be increased with higher turbine inlet with higher turbine inlet temperatures temperatures

•• Advanced gas turbines are operated Advanced gas turbines are operated at peak turbine inlet temperature at peak turbine inlet temperature about about 17001700 °°C, C, which is well beyond which is well beyond the maximum endurable temperature the maximum endurable temperature for the blade material. for the blade material.


Damaged turbine blades

•• Protect the blade against the risk of damageProtect the blade against the risk of damage–– New material to endure higher temperatureNew material to endure higher temperature–– StateState--ofof--art cooling techniques for film cooing and trailing edge coolingart cooling techniques for film cooing and trailing edge cooling

Majority of Majority of damages starting damages starting at tips and at tips and trailing edgestrailing edges


Experimental SetupExperimental Setup

Not on scale


Raw Images for cooling effectiveness

Black image Reference Image

Air image Nitrogen image

116


X/H

Z/H

0 2 4 6 8

-2

0

210.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050

C.E.M=0.43

X/H

Z/H

0 2 4 6 8

-2

0

210.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050

C.E.M=1.6

Cooling EffectivenessCooling Effectiveness measurements by using PSP techniquemeasurements by using PSP technique


Cooling EffectivenessCooling Effectiveness Measurements by using PSP techniqueMeasurements by using PSP technique

-3

-2

-1

0

1

2

3

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1

M=1.6M=1.1M=0.76M=0.64M=0.52M=0.43M=0.25

X/H=4

Cooling Effectiveness η

Z/H

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5 6 7 8 9

M=1.6M=1.1M=0.76M=0.64M=0.52M=0.43M=0.25

X/H

Coo

ling

Effe

ctiv

enes

s η

X/H

Z/H

0 2 4 6 8

-2

0

210.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050

C.E.M=0.43

X/H

Z/H

0 2 4 6 8

-2

0

210.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050

C.E.M=0.52

X/H

Z/H

0 2 4 6 8

-2

0

210.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.05

C.E.M=0.64

X/H

Z/H

0 2 4 6 8

-2

0

210.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050

C.E.M=0.76

X/H

Z/H

0 2 4 6 8

-2

0

2

10.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.05

C.E.M=1.1

X/H

Z/H

0 2 4 6 8

-2

0

210.950.90.850.80.750.70.650.60.550.50.450.40.350.30.250.20.150.10.050

C.E.M=1.6

118


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