Instrumentation, Measurements, and Experiments in Fluids

504 Pages·2007·4.27 MB·English

by  E. Rathakrishnan

Instrumentation,
Measurements,
and Experiments
in Fluids
E. Rathakrishnan
Instrumentation,
Measurements,
and Experiments
in Fluids

Boca Raton London New York
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Version Date: 20130916
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Dedication
Thisbookisdedicatedtomyparents,
Mr.ThammanurShunmugamEthirajan
and
Mrs.AandaalEthirajan
E.Rathakrishnan
Contents
Preface.................................................................xix
AbouttheBook........................................................xxiii
AbouttheAuthor......................................................xxv
1 NeedandObjectiveofExperimentalStudy..........................1
1.1 Introduction....................................................1
1.2 SomeFluidMechanicsMeasurements...........................1
1.2.1 WindTunnelStudies....................................2
1.2.2 AnalogueMethods......................................2
1.2.3 FlowVisualization......................................2
1.3 MeasurementSystems..........................................3
1.3.1 SensingElement........................................3
1.3.2 SignalConverter........................................3
1.3.3 Display.................................................3
1.3.3.1 PerformanceTerms.............................4
1.4 SomeoftheImportantQuantitiesAssociatedwithFluid
FlowMeasurements............................................5
1.5 Summary.......................................................6
2 FundamentalsofFluidMechanics....................................9
2.1 Introduction....................................................9
2.2 PropertiesofFluids.............................................9
2.2.1 Pressure...............................................10
2.2.2 Temperature...........................................11
2.2.3 Density................................................11
2.2.4 Viscosity...............................................12
2.2.5 AbsoluteCoefficientofViscosity.......................12
2.2.6 KinematicViscosityCoefficient........................15
2.2.7 ThermalConductivityofAir...........................15
2.2.8 Compressibility........................................16
2.3 ThermodynamicProperties....................................16
2.3.1 SpecificHeat...........................................17
2.3.2 TheRatioofSpecificHeats.............................17
2.4 SurfaceTension................................................18
2.5 AnalysisofFluidFlow.........................................19
2.5.1 RelationBetweenLocalandMaterialRates
ofChange ............................................. 20
2.5.2 GraphicalDescriptionofFluidMotion.................21
2.5.2.1 Pathline.......................................22
2.5.2.2 Streakline.....................................22
2.5.2.3 Streamlines....................................22
2.5.2.4 Timelines......................................22
2.6 BasicandSubsidiaryLawsforContinuousMedia..............23
2.6.1 SystemsandControlVolumes..........................23
2.6.2 IntegralandDifferentialAnalysis......................23
2.6.3 StateEquation.........................................24
2.7 KinematicsofFluidFlow......................................24
2.7.1 BoundaryLayerThickness.............................27
2.7.2 DisplacementThickness...............................27
2.7.3 TransitionPoint........................................29
2.7.4 SeparationPoint.......................................29
2.7.5 RotationalandIrrotationalMotion.....................29
2.8 Streamlines....................................................30
2.8.1 RelationshipBetweenStreamFunctionand
VelocityPotential......................................31
2.9 PotentialFlow.................................................31
2.9.1 Two-DimensionalSourceandSink.....................33
2.9.2 SimpleVortex..........................................34
2.9.3 Source–SinkPair.......................................35
2.10 ViscousFlows.................................................36
2.10.1 DragofBodies.........................................38
2.10.1.1 PressureDrag................................38
2.10.1.2 SkinFrictionDrag............................40
2.10.1.3 ComparisonofDragofVariousBodies........41
2.10.2 Turbulence............................................42
2.10.3 FlowThroughPipes...................................49
2.11 GasDynamics.................................................53

2.11.1 PerfectGas............................................53
2.11.2 VelocityofSound......................................54
2.11.3 MachNumber.........................................55
2.11.4 FlowwithAreaChange................................55
2.11.4.1 IsentropicRelations..........................55
2.11.4.2 Area–MachNumberRelation.................56
2.11.4.3 Prandtl–MeyerFunction......................56
2.11.5 NormalShockRelations................................57
2.11.6 ObliqueShockRelations...............................58
2.11.7 FlowwithFriction.....................................59
2.11.7.1 WorkingFormulaeforFanno-TypeFlow......59
2.11.8 FlowwithSimpleT -Change...........................61
0
2.11.8.1 WorkingFormulaeforRayleigh-TypeFlow...61
2.12 Summary......................................................62
3 WindTunnels.......................................................73
3.1 Introduction...................................................73
3.1.1 Low-SpeedWindTunnels..............................73
3.1.2 High-SpeedWindTunnels.............................74
3.1.2.1 GeneralFeatures..............................75
3.1.2.2 TheEffuser....................................75
3.1.2.3 Test-Section...................................75
3.1.2.4 Diffuser.......................................75
3.1.2.5 DrivingUnit..................................75
3.1.3 Special-PurposeTunnels...............................76
3.2 Low-SpeedWindTunnels......................................76
3.2.1 Effuser ................................................76
3.2.2 Test-Section............................................76
3.2.3 Diffuser...............................................77
3.2.4 DrivingUnit...........................................77
3.3 PowerLossesinaWindTunnel................................77
3.3.1 CalculationofPercentageEnergyLossintheVarious
PartsofWindTunnel..................................77
3.3.1.1 EnergyRatio..................................78
3.3.1.2 LossesinCylindricalSection...................79
3.3.1.3 LossesinConvergentCone....................80
3.3.1.4 LossesinDiffuser.............................81
3.3.1.5 Honeycombs..................................83
3.3.1.6 GuideVanes...................................84
3.3.1.7 LossesDuetoOpen-JetTest-Section...........85
3.3.1.8 Screens(WireGauze)..........................86
3.4 High-SpeedWindTunnels.....................................90
3.4.1 Blowdown-TypeWindTunnels ........................ 91
3.4.1.1 Advantages...................................91
3.4.1.2 Disadvantages................................92
3.4.2 Induction-TypeTunnels................................92
3.4.2.1 Advantages...................................92
3.4.2.2 Disadvantages................................93
3.4.3 ContinuousSupersonicWindTunnels..................93
3.4.4 LossesinSupersonicTunnels..........................95
3.4.5 SupersonicWindTunnelDiffusers.....................96
3.4.5.1 PolytropicEfficiency...........................97
3.4.5.2 IsentropicEfficiency...........................97
3.4.6 EffectsofSecondThroat...............................98
3.4.7 CompressorTunnelMatching.........................101
3.4.7.1 BasicFormulaeforSupersonicWind
TunnelCalculations..........................104
3.4.8 TheMassFlow.......................................105
3.4.9 BlowdownTunnelOperation.........................109
3.4.9.1 ReynoldsNumberControl....................111
3.4.10 OptimumConditions.................................113
3.4.11 RunningTimeofBlowdownWindTunnels............114
3.5 HypersonicTunnels..........................................116
3.5.1 HypersonicNozzle...................................119
3.6 InstrumentationandCalibrationofWindTunnels.............119
3.6.1 Low-SpeedWindTunnels.............................120
3.6.2 SpeedSetting.........................................120
3.6.3 FlowDirection........................................121
3.6.3.1 YawSphere..................................122
3.6.3.2 ClawYawMeter.............................123
3.6.4 Turbulence...........................................124
3.6.4.1 TurbulenceSphere...........................124
3.6.4.2 PressureSphere..............................126
3.6.4.3 LimitationsofTurbulenceSphere.............128
3.6.5 Hot-WireAnemometer...............................128
3.6.6 Rakes.................................................129
3.6.7 Surging...............................................129
3.7 WindTunnelBalance.........................................130
3.7.1 WireBalances.........................................131
3.7.2 Strut-TypeBalances...................................132
3.7.3 Platform-TypeBalance................................133
3.7.4 Yoke-TypeBalance....................................134
3.7.5 Pyramid-TypeBalance................................135
3.7.6 Strain-GaugeBalance.................................135
3.7.6.1 Strain-GaugeOperationTheory..............136
3.7.6.2 BasicEquationsofStrain-Gauge
Transducer...................................139
3.7.6.3 Strain-GaugeSignal-MeasuringDevices......139
3.7.6.4 BalancingBridge.............................140
3.7.7 BalanceCalibration...................................140
3.7.8 WindTunnelBoundaryCorrection....................141
3.8 CalibrationofSupersonicWindTunnels......................142
3.8.1 Calibration...........................................144

3.8.2 MachNumberDetermination.........................144
3.8.3 PitotPressureMeasurement..........................145
3.8.4 StaticPressureMeasurement..........................145
3.8.5 DeterminationofFlowAngularity....................146
3.8.6 DeterminationofTurbulenceLevel....................146
3.8.7 DeterminationofTest-SectionNoise..................147
3.8.8 TheUseofCalibrationResults........................147
3.8.9 StartingofSupersonicTunnels........................148
3.8.10 StartingLoads........................................148
3.8.11 ReynoldsNumberEffects.............................149
3.8.12 ModelMounting-StingEffects........................149
3.9 CalibrationandUseofHypersonicTunnels...................149
3.9.1 CalibrationofHypersonicTunnels....................150
3.9.2 MachNumberDetermination.........................150
3.9.3 DeterminationofFlowAngularity....................153
3.9.4 DeterminationofTurbulenceLevel....................153
3.9.4.1 BlockageTests................................153
3.9.4.2 StartingLoads................................153
3.9.5 ReynoldsNumberEffects.............................153
3.9.6 ForceMeasurements..................................154
3.10 FlowVisualization............................................155
3.11 HypervelocityFacilities.......................................155
3.11.1 HotshotTunnels......................................156
3.11.2 PlasmaArcTunnels...................................157
3.11.3 ShockTubes..........................................158
3.11.4 ShockTunnels........................................159
3.11.5 GunTunnels..........................................160
3.12 LudwiegTube................................................161
3.12.1 OperatingPrincipleofLudwiegTube
(Koppenwallner,2000)................................162
3.12.2 SomeSpecificAdvantagesandDisadvantages
ofLudwiegTube......................................164
3.12.2.1 AdvantagesofLudwiegTubeTunnel
ComparedtoStandardBlowdown
Tunnels.....................................164
3.12.2.2 DisadvantagesofLudwiegTubeTunnel.....165
3.12.3 HypersonicSimulationRequirements.................165
3.12.3.1 Mach–ReynoldsSimulationfor
CompressibilityandViscousEffects.........166
3.12.3.2 SimulationofRealGasEffects...............166
3.12.3.3 IndustrialTunnels...........................167
3.12.3.4 ResearchTunnels............................167
3.12.4 PressureMeasuringSystem...........................167
3.13 Summary ....................................................167
4 FlowVisualization.................................................175
4.1 Introduction..................................................175
4.2 VisualizationTechniques.....................................175
4.2.1 SmokeTunnel........................................176
4.2.1.1 SmokeProductionMethods..................177
4.2.1.2 WoodSmoke.................................177
4.2.1.3 KeroseneSmokeGenerator...................178
4.2.2 DesignofSmokeTunnel..............................180
4.2.2.1 ApplicationofSmokeVisualization...........182
4.3 CompressibleFlows..........................................184
4.3.1 Interferometer........................................185
4.3.1.1 FormationofInterferencePatterns............185
4.3.1.2 QuantitativeEvaluation......................187
4.3.2 Fringe-DisplacementMethod.........................189
4.3.3 SchlierenSystem......................................189
4.3.4 RangeandSensitivityoftheSchlierenSystem.........193
4.3.5 OpticalComponents’QualityRequirements..........193
4.3.5.1 SchlierenMirrors.............................193
4.3.5.2 LightSource.................................194
4.3.5.3 CondenserLens..............................194
4.3.5.4 FocusingLens................................194
4.3.5.5 Knife-Edge...................................194
4.3.5.6 ColorSchlieren...............................194
4.3.5.7 ShortDurationLightSource..................195
4.3.6 SensitivityoftheSchlierenMethodforShock
andExpansionStudies................................197
4.3.7 Shadowgraph........................................199
4.3.8 ComparisonofSchlieren
andShadowgraphMethods...........................201
4.4 Summary ....................................................201
5 Hot-WireAnemometry.............................................203
5.1 Introduction..................................................203
5.2 OperatingPrinciple...........................................203
5.3 Hot-WireFilaments...........................................204
5.4 ConstantCurrentHot-WireAnemometerCCA................209
5.4.1 MeanVelocityMeasurements.........................209
5.4.2 FluctuatingVelocityMeasurements...................210
5.4.3 ThermalInertiaofHot-Wire..........................212
5.4.4 RMSMeasurementsoftheFluctuatingVelocities......213
5.4.5 MeasurementofVelocityComponents................214
5.4.6 MeasurementofTemperaturebyConstant
CurrentMethod......................................215
5.4.7 MeasurementofSteady-StateTemperature............215
5.4.8 MeasurementofTemperatureFluctuations............215
5.5 ConstantTemperatureHot-WireAnemometers...............216
5.5.1 RelationBetweenFlowVelocity
andOutputVoltage...................................217
5.6 Hot-WireProbes..............................................218
5.7 Hot-WireBridgeforClassroomDemonstration...............220
5.7.1 Hot-WireBridgeOperatingProcedure................221
5.7.2 ANoteofCaution....................................221
5.8 EffectofCompressibility......................................222
5.9 LimitationsofHot-WireAnemometer.........................223
5.10 Summary ....................................................224
6 AnalogueMethods.................................................229
6.1 Introduction..................................................229
6.2 Hele–ShawApparatus........................................229
6.2.1 BasicEquationsofHele–ShawAnalogy...............233
6.3 ElectrolyticTank..............................................235