Preface ....................................................... xix
About the Book .............................................. xxiii
About the Author ............................................. xxv
1 Need and Objective of Experimental Study ..................... 1
1.1 Introduction .......................................... 1
1.2 Some Fluid Mechanics Measurements ..................... 1
1.2.1 Wind Tunnel Studies ............................ 2
1.2.2 Analogue Methods ............................... 2
1.2.3 Flow Visualization ............................. 2
1.3 Measurement Systems ................................... 3
1.3.1 Sensing Element ................................ 3
1.3.2 Signal Converter ............................... 3
1.3.3 Display ........................................ 3
1.3.3.1 Performance Terms ..................... 4
1.4 Some of the Important Quantities
Associated with Fluid Flow Measurements ............... 5
1.5 Summary ............................................... 6
2 Fundamentals of Fluid Mechanics .............................. 9
2.1 Introduction .......................................... 9
2.2 Properties of Fluids .................................. 9
2.2.1 Pressure ...................................... 10
2.2.2 Temperature ................................... 11
2.2.3 Density ....................................... 11
2.2.4 Viscosity ..................................... 12
2.2.5 Absolute Coefficient of Viscosity ............. 12
2.2.6 Kinematic Viscosity Coefficient ............... 15
2.2.7 Thermal Conductivity of Air ................... 15
2.2.8 Compressibility ............................... 16
2.3 Thermodynamic Properties ............................. 16
2.3.1 Specific Heat ................................. 17
2.3.2 The Ratio of Specific Heats ................... 17
2.4 Surface Tension ...................................... 18
2.5 Analysis of Fluid Flow ............................... 19
2.5.1 Relation Between Local and Material Rates
of Change ..................................... 20
2.5.2 Graphical Description of Fluid Motion ......... 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 Basic and Subsidiary Laws for Continuous Media ....... 23
2.6.1 Systems and Control Volumes ................... 23
2.6.2 Integral and Differential Analysis ............ 23
2.6.3 State Equation ................................ 24
2.7 Kinematics of Fluid Flow ............................. 24
2.7.1 Boundary Layer Thickness ...................... 27
2.7.2 Displacement Thickness ........................ 27
2.7.3 Transition Point .............................. 29
2.7.4 Separation Point .............................. 29
2.7.5 Rotational and Irrotational Motion ............ 29
2.8 Streamlines .......................................... 30
2.8.1 Relationship Between Stream Function and
Velocity Potential ............................ 31
2.9 Potential Flow ....................................... 31
2.9.1 Two-Dimensional Source and Sink ............... 33
2.9.2 Simple Vortex ................................. 34
2.9.3 Source-Sink Pair .............................. 35
2.10 Viscous Flows ........................................ 36
2.10.1 Drag of Bodies ................................ 38
2.10.1.1 Pressure Drag ........................ 38
2.10.1.2 Skin Friction Drag ................... 40
2.10.1.3 Comparison of Drag of Various
Bodies ............................... 41
2.10.2 Turbulence .................................... 42
2.10.3 Flow Through Pipes ............................ 49
2.11 Gas Dynamics ......................................... 53
2.11.1 Perfect Gas ................................... 53
2.11.2 Velocity of Sound ............................. 54
2.11.3 Mach Number ................................... 55
2.11.4 Flow with Area Change ......................... 55
2.11.4.1 Isentropic Relations ................. 55
2.11.4.2 Area-Mach Number Relation ............ 56
2.11.4.3 Prandtl-Meyer Function ............... 56
2.11.5 Normal Shock Relations ....................... 57
2.11.6 Oblique Shock Relations ...................... 58
2.11.7 Flow with Friction ........................... 59
2.11.7.1 Working Formulae for Fanno-Type
Flow ............................... 59
2.11.8 Flow with Simple To-Change ................... 61
2.11.8.1 Working Formulae for
Rayleigh-Type Flow ................. 61
2.12 Summary .............................................. 62
3 Wind Tunnels ................................................ 73
3.1 Introduction ......................................... 73
3.1.1 Low-Speed Wind Tunnels ........................ 73
3.1.2 High-Speed Wind Tunnels ....................... 74
3.1.2.1 General Features ..................... 75
3.1.2.2 The Effuser .......................... 75
3.1.2.3 Test-Section ......................... 75
3.1.2.4 Diffuser ............................. 75
3.1.2.5 Driving Unit ......................... 75
3.1.3 Special-Purpose Tunnels ....................... 76
3.2 Low-Speed Wind Tunnels ............................... 76
3.2.1 Effuser ....................................... 76
3.2.2 Test-Section .................................. 76
3.2.3 Diffuser ...................................... 77
3.2.4 Driving Unit .................................. 77
3.3 Power Losses in a Wind Tunnel ........................ 77
3.3.1 Calculation of Percentage Energy Loss in the
Various Parts of Wind Tunnel .................. 77
3.3.1.1 Energy Ratio ......................... 78
3.3.1.2 Losses in Cylindrical Section ........ 79
3.3.1.3 Losses in Convergent Cone ............ 80
3.3.1.4 Losses in Diffuser ................... 81
3.3.1.5 Honeycombs ........................... 83
3.3.1.6 Guide Vanes .......................... 84
3.3.1.7 Losses Due to Open-Jet
Test-Section ......................... 85
3.3.1.8 Screens (Wire Gauze) ................. 86
3.4 High-Speed Wind Tunnels .............................. 90
3.4.1 Blowdown-Type Wind Tunnels .................... 91
3.4.1.1 Advantages ........................... 91
3.4.1.2 Disadvantages ........................ 92
3.4.2 Induction-Type Tunnels ........................ 92
3.4.2.1 Advantages ........................... 92
3.4.2.2 Disadvantages ........................ 93
3.4.3 Continuous Supersonic Wind Tunnels ............ 93
3.4.4 Losses in Supersonic Tunnels .................. 95
3.4.5 Supersonic Wind Tunnel Diffusers .............. 96
3.4.5.1 Polytropic Efficiency ................ 97
3.4.5.2 Isentropic Efficiency ................ 97
3.4.6 Effects of Second Throat ...................... 98
3.4.7 Compressor Tunnel Matching ................... 101
3.4.7.1 Basic Formulae for Supersonic Wind
Tunnel Calculations ................. 104
3.4.8 The Mass Flow ................................ 105
3.4.9 Blowdown Tunnel Operation .................... 109
3.4.9.1 Reynolds Number Control ............. 111
3.4.10 Optimum Conditions .......................... 113
3.4.11 Running Time of Blowdown Wind Tunnels ....... 114
3.5 Hypersonic Tunnels .................................. 116
3.5.1 Hypersonic Nozzle ............................ 119
3.6 Instrumentation and Calibration of Wind Tunnels ..... 119
3.6.1 Low-Speed Wind Tunnels ....................... 120
3.6.2 Speed Setting ................................ 120
3.6.3 Flow Direction ............................... 121
3.6.3.1 Yaw Sphere .......................... 122
3.6.3.2 Claw Yaw Meter ...................... 123
3.6.4 Turbulence ................................... 124
3.6.4.1 Turbulence Sphere ................... 124
3.6.4.2 Pressure Sphere ..................... 126
3.6.4.3 Limitations of Turbulence Sphere .... 128
3.6.5 Hot-Wire Anemometer .......................... 128
3.6.6 Rakes ........................................ 129
3.6.7 Surging ...................................... 129
3.7 Wind Tunnel Balance ................................. 130
3.7.1 Wire Balances ................................ 131
3.7.2 Strut-Type Balances .......................... 132
3.7.3 Platform-Type Balance ........................ 133
3.7.4 Yoke-Type Balance ............................ 134
3.7.5 Pyramid-Type Balance ......................... 135
3.7.6 Strain-Gauge Balance ......................... 135
3.7.6.1 Strain-Gauge Operation Theory ....... 136
3.7.6.2 Basic Equations of Strain-Gauge
Transducer .......................... 139
3.7.6.3 Strain-Gauge Signal-Measuring
Devices ............................. 139
3.7.6.4 Balancing Bridge .................... 140
3.7.7 Balance Calibration .......................... 140
3.7.8 Wind Tunnel Boundary Correction .............. 141
3.8 Calibration of Supersonic Wind Tunnels .............. 142
3.8.1 Calibration .................................. 144
3.8.2 Mach Number Determination .................... 144
3.8.3 Pitot Pressure Measurement ................... 145
3.8.4 Static Pressure Measurement .................. 145
3.8.5 Determination of Flow Angularity ............. 146
3.8.6 Determination of Turbulence Level ............ 146
3.8.7 Determination of Test-Section Noise .......... 147
3.8.8 The Use of Calibration Results ............... 147
3.8.9 Starting of Supersonic Tunnels ............... 148
3.8.10 Starting Loads ............................... 148
3.8.11 Reynolds Number Effects ...................... 149
3.8.12 Model Mounting-Sting Effects ................. 149
3.9 Calibration and Use of Hypersonic Tunnels ........... 149
3.9.1 Calibration of Hypersonic Tunnels ............ 150
3.9.2 Mach Number Determination .................... 150
3.9.3 Determination of Flow Angularity ............. 153
3.9.4 Determination of Turbulence Level ............ 153
3.9.4.1 Blockage Tests ...................... 153
3.9.4.2 Starting Loads ...................... 153
3.9.5 Reynolds Number Effects ...................... 153
3.9.6 Force Measurements ........................... 154
3.10 Flow Visualization .................................. 155
3.11 Hypervelocity Facilities ............................ 155
3.11.1 Hotshot Tunnels .............................. 156
3.11.2 Plasma Arc Tunnels ........................... 157
3.11.3 Shock Tubes .................................. 158
3.11.4 Shock Tunnels ................................ 159
3.11.5 Gun Tunnels .................................. 160
3.12 Ludwieg Tube ........................................ 161
3.12.1 Operating Principle of Ludwieg Tube
(Koppenwallner, 2000) ........................ 162
3.12.2 Some Specific Advantages and Disadvantages
of Ludwieg Tube .............................. 164
3.12.2.1 Advantages of Ludwieg Tube Tunnel
Compared to Standard Blowdown
Tunnels ............................. 164
3.12.2.2 Disadvantages of Ludwieg Tube
Tunnel .............................. 165
3.12.3 Hypersonic Simulation Requirements ........... 165
3.12.3.1 Mach-Reynolds Simulation for
Compressibility and Viscous
Effects ............................. 166
3.12.3.2 Simulation of Real Gas Effects ...... 166
3.12.3.3 Industrial Tunnels .................. 167
3.12.3.4 Research Tunnels .................... 167
3.12.4 Pressure Measuring System ................... 167
3.13 Summary ............................................. 167
4 Flow Visualization ......................................... 175
4.1 Introduction ........................................ 175
4.2 Visualization Techniques ............................ 175
4.2.1 Smoke Tunnel ................................. 176
4.2.1.1 Smoke Production Methods ............ 177
4.2.1.2 Wood Smoke .......................... 177
4.2.1.3 Kerosene Smoke Generator ............ 178
4.2.2 Design of Smoke Tunnel ....................... 180
4.2.2.1 Application of Smoke
Visualization ....................... 182
4.3 Compressible Flows .................................. 184
4.3.1 Interferometer ............................... 185
4.3.1.1 Formation of Interference
Patterns ............................ 185
4.3.1.2 Quantitative Evaluation ............. 187
4.3.2 Fringe-Displacement Method ................... 189
4.3.3 Schlieren System ............................. 189
4.3.4 Range and Sensitivity of the Schlieren
System ....................................... 193
4.3.5 Optical Components' Quality Requirements ..... 193
4.3.5.1 Schlieren Mirrors ................... 193
4.3.5.2 Light Source ........................ 194
4.3.5.3 Condenser Lens ...................... 194
4.3.5.4 Focusing Lens ....................... 194
4.3.5.5 Knife-Edge .......................... 194
4.3.5.6 Color Schlieren ..................... 194
4.3.5.7 Short Duration Light Source ......... 195
4.3.6 Sensitivity of the Schlieren Method for
Shock and Expansion Studies .................. 197
4.3.7 Shadowgraph .................................. 199
4.3.8 Comparison of Schlieren and Shadowgraph
Methods ...................................... 201
4.4 Summary ............................................. 201
5 Hot-Wire Anemometry ........................................ 203
5.1 Introduction ........................................ 203
5.2 Operating Principle ................................. 203
5.3 Hot-Wire Filaments .................................. 204
5.4 Constant Current Hot-Wire Anemometer CCA ............ 209
5.4.1 Mean Velocity Measurements ................... 209
5.4.2 Fluctuating Velocity Measurements ............ 210
5.4.3 Thermal Inertia of Hot-Wire .................. 212
5.4.4 RMS Measurements of the Fluctuating
Velocities ................................... 213
5.4.5 Measurement of Velocity Components ........... 214
5.4.6 Measurement of Temperature by Constant
Current Method ............................... 215
5.4.7 Measurement of Steady-State Temperature ...... 215
5.4.8 Measurement of Temperature Fluctuations ...... 215
5.5 Constant Temperature Hot-Wire Anemometers ........... 216
5.5.1 Relation Between Flow Velocity and Output
Voltage ...................................... 217
5.6 Hot-Wire Probes ..................................... 218
5.7 Hot-Wire Bridge for Classroom Demonstration ......... 220
5.7.1 Hot-Wire Bridge Operating Procedure .......... 221
5.7.2 A Note of Caution ............................ 221
5.8 Effect of Compressibility ........................... 222
5.9 Limitations of Hot-Wire Anemometer .................. 223
5.10 Summary ............................................. 224
6 Analogue Methods ........................................... 229
6.1 Introduction ........................................ 229
6.2 Hele-Shaw Apparatus ................................. 229
6.2.1 Basic Equations of Hele-Shaw Analogy ......... 233
6.3 Electrolytic Tank ................................... 235
6.4 Hydraulic Analogy ................................... 238
6.4.1 Theory of the Analogy ........................ 239
6.4.1.1 Shallow Water Flow .................. 239
6.4.1.2 Gas Flow ............................ 240
6.5 Hydraulic Jumps (Shocks) ............................ 243
6.5.1 General Equations for Attached Oblique
Shocks ....................................... 245
6.5.2 General Equations for Slant (Oblique)
Attached Hydraulic Jumps ..................... 245
6.5.3 Limitation of the Analogy .................... 246
6.5.3.1 Two-Dimensionality .................. 246
6.5.3.2 Specific Heats Ratio ................ 246
6.5.3.3 Velocity of Wave Propagation ........ 246
6.5.3.4 Vertical Accelerations .............. 247
6.5.3.5 Viscosity and Heat Conductivity ..... 248
6.5.3.6 Surface Tension ..................... 248
6.5.3.7 Appropriate Technique for
Different Types of Problems ......... 248
6.5.4 Depth Measurement ............................ 249
6.6 Velocity Measurement ................................ 250
6.7 Experimental Study .................................. 250
6.7.1 Towing Tank .................................. 251
6.7.1.1 Flow Past Shockless Lifting and
Nonlifting Airfoils ................. 251
6.7.2 Streamline Similarity and Transonic
Similarity Rule .............................. 253
6.8 Application of the Hydraulic Analogy
to Supersonic Airfoils .............................. 255
6.8.1 Aerodynamic Forces on Airfoils ............... 255
6.8.2 Hydrodynamic Forces on Airfoils .............. 255
6.8.3 Measurements with a Semi-Wedge Airfoil ....... 255
6.9 Experimental Study .................................. 256
6.10 Summary ............................................. 259
7 Pressure-Measurement Techniques ............................ 263
7.1 Introduction ........................................ 263
7.1.1 Pressure-Measuring Devices ................... 263
7.1.2 Principle of Manometer ....................... 264
7.2 Barometers .......................................... 264
7.2.1 Syphon Barometer ............................. 266
7.2.2 Fortin Barometer ............................. 266
7.2.3 Aneroid Barometer ............................ 268
7.3 Manometers .......................................... 268
7.3.1 Inclined Manometer ........................... 271
7.3.2 Micro Manometer .............................. 273
7.3.3 Betz Manometer ............................... 273
7.4 Dial-Type Pressure Gauge ............................ 274
7.5 Pressure Transducers ................................ 276
7.5.1 Linear Variable Differential Transformer
LVDT ......................................... 278
7.5.2 Capacitance Pickup ........................... 279
7.5.3 Optical-Type Pressure Transducer ............. 279
7.6 Pitot, Static, and Pitot-Static Tubes ............... 280
7.6.1 Dynamic Head Measurement ..................... 281
7.6.1.1 Incompressible Flow ................. 282
7.7 Pitot-Static Tube Characteristics ................... 287
7.7.1 Pitot-Static Tube Limitations ................ 291
7.8 Factors Influencing Pitot-Static Tube Performance ... 291
7.8.1 Turbulence Effect ............................ 292
7.8.2 Velocity Gradient Effect ..................... 292
7.8.3 Viscosity Effects ............................ 293
7.8.4 Vibration Effect on Pitot-Static Probe
Measurements ................................. 293
7.8.5 Misalignment Effect .......................... 295
7.9 Pitot Probes ........................................ 295
7.10 Static Probes ....................................... 296
7.11 Pitot-Static Probes ................................. 296
7.12 Yaw Effect in Compressible Flow ..................... 297
7.13 Static Pressure Measurement in Compressible Flows ... 297
7.14 Determination of Flow Direction ..................... 299
7.14.1 Yaw Sphere .................................. 301
7.14.2 Claw Yaw Probe .............................. 302
7.14.3 Three-Hole and Five-Hole Yaw Probes ......... 302
7.14.4 Cobra Probe ................................. 303
7.15 Low-Pressure Measurement ............................ 304
7.15.1 The McLeod Gauge ............................ 304
7.15.2 Pirani Gauge ................................ 306
7.15.3 Knudsen Gauge ............................... 308
7.15.4 Ionization Gauge ............................ 309
7.16 Preston and Stanton Tubes ........................... 309
7.17 Sound Measurements .................................. 310
7.17.1 Introduction ................................ 310
7.17.2 Sound and Noise ............................. 310
7.17.3 Pure Tone ................................... 312
7.17.4 Broadband and White Noise ................... 312
7.17.5 Sound Units ................................. 312
7.17.6 Human Hearing Limits ........................ 313
7.17.7 Impulse Sound ............................... 314
7.18 Dynamic Pressure Gauges ............................. 315
7.19 Summary ............................................. 317
8 Velocity Measurements ...................................... 323
8.1 Introduction ........................................ 323
8.2 Velocity and Mach Number from Pressure
Measurements ........................................ 323
8.3 Laser Doppler Anemometer ............................ 325
8.3.1 LDA Principle ................................ 325
8.3.2 Doppler Shift Equation ....................... 326
8.3.3 Reference Beam System ........................ 328
8.3.4 Fringe System ................................ 328
8.4 Measurement of Velocity by Hot-Wire Anemometer ...... 329
8.5 Measurement of Velocity Using Vortex-Shedding
Technique ........................................... 329
8.6 Fluid-Jet Anemometer ................................ 331
8.7 Summary ............................................. 332
9 Temperature Measurement .................................... 335
9.1 Introduction ........................................ 335
9.2 Temperature Scales .................................. 335
9.2.1 The International Practical Temperature
Scale ........................................ 337
9.3 Temperature Measurement ............................. 338
9.3.1 Fluid Thermometers ........................... 338
9.3.1.1 Mercury-in-Glass Thermometer ........ 338
9.3.2 Beckmann Thermometer ......................... 339
9.3.3 Gas Thermometer .............................. 340
9.3.4 Temperature Gauges Using Fluids .............. 342
9.4 Temperature Measurement by Thermal Expansion ........ 343
9.4.1 Bimetallic Thermometers ...................... 343
9.5 Temperature Measurements by Electrical Effects ...... 345
9.5.1 Thermocouples ................................ 346
9.5.2 Measurement of Thermocouple Voltage .......... 346
9.5.2.1 External Reference Junction ......... 350
9.5.2.2 Software Compensation ............... 352
9.5.2.3 Hardware Compensation ............... 352
9.5.2.4 Voltage-to-Temperature Conversion ... 353
9.5.2.5 Noise Rejection ..................... 358
9.5.2.6 Tree Switching ...................... 359
9.5.2.7 Analogue Filter ..................... 359
9.5.2.8 Integration ......................... 359
9.5.2.9 Guarding ............................ 359
9.6 Practical Thermocouple Measurements ................. 359
9.6.1 Poor Junction Connections .................... 360
9.6.2 Decalibration ................................ 360
9.6.3 Shunt Impedance .............................. 360
9.6.4 Galvanic Action .............................. 361
9.6.5 Thermal Shunting ............................. 361
9.6.6 Wire Calibration ............................. 362
9.6.7 Documentation ................................ 362
9.6.8 Diagnostics .................................. 362
9.6.8.1 Event Record ........................ 362
9.6.8.2 Zone Box Test ....................... 363
9.6.9 Thermocouple Resistance ...................... 364
9.7 The Resistance Temperature Detector ................. 364
9.7.1 Metal Film RTDs .............................. 366
9.7.1.1 Resistance Measurements ............. 366
9.7.1.2 Four-Wire Ohms ...................... 368
9.7.2 Measurement Errors with Three-Wire Bridge .... 368
9.7.3 Resistance to Temperature Conversion ......... 369
9.7.3.1 Protection .......................... 370
9.7.3.2 Self-Heating ........................ 370
9.7.3.3 Thermal Shunting .................... 370
9.7.3.4 Thermal EMF ......................... 370
9.7.4 Thermistors .................................. 370
9.7.4.1 Measurement with Thermistor ......... 372
9.8 Temperature Measurement with Pyrometers ............. 372
9.8.1 Optical Pyrometer ............................ 372
9.8.2 Radiation Pyrometer .......................... 373
9.8.3 Infrared Thermography ........................ 374
9.8.4 Fusion Pyrometers ............................ 374
9.8.5 Thermal Paints ............................... 375
9.9 Temperature Measurement in Fluid Flows .............. 375
9.9.1 Static Temperature Determination ............. 377
9.9.2 Total Temperature Measurement ................ 377
9.10 Temperature-Measuring Problems in Fluid Flows ....... 378
9.10.1 Conduction Error ............................. 378
9.10.2 Radiation Error .............................. 380
9.11 Dynamic Response of Temperature Sensors ............. 381
9.12 Summary ............................................. 383
10 Measurement of Wall Shear Stress ........................... 389
10.1 Introduction ........................................ 389
10.2 Measurement Methods ................................. 390
10.2.1 Floating Element Method ...................... 390
10.2.2 Momentum Integral Method ..................... 391
10.2.3 Preston Tube ................................. 391
10.2.4 Fence Technique .............................. 393
10.2.5 Heat Transfer Gauge .......................... 394
10.2.6 Law of the Wall .............................. 395
10.3 Summary ............................................. 396
11 Mass and Volume Flow Measurements .......................... 399
11.1 Introduction ........................................ 399
11.2 Direct Methods ...................................... 400
11.2.1 Tanks ........................................ 400
11.2.2 Displacement Meters .......................... 400
11.3 Indirect Methods .................................... 402
11.3.1 Variable-Head Meters ......................... 402
11.3.2 Some Practical Details of Obstruction
Meters ....................................... 407
11.3.3 Sonic Nozzle ................................. 412
11.3.4 Pitot Tubes .................................. 413
11.3.5 Rotameters ................................... 414
11.3.6 Drag-Body Meters ............................. 415
11.3.7 Ultrasonic Flow Meters ....................... 416
11.3.8 Vortex-Shedding Flow Meters .................. 418
11.3.9 Measurement of Gross Mass Flow Rate .......... 419
11.4 Volume Flow Meter ................................... 420
11.4.1 Direct Mass Flow Meters ...................... 422
11.5 Summary ............................................. 423
12 Special Flows .............................................. 429
12.1 Introduction ........................................ 429
12.2 Geophysical Flows ................................... 429
12.2.1 Rotating Tank ................................ 430
12.3 Experiment on Taylor-Proudman Theorem ............... 430
12.5 Experiment on Spin-Up and Spin-Down ................. 432
12.6 Transition and Reverse Transition ................... 433
12.6.1 Transition in a Channel Flow -
A Visualization .............................. 435
12.6.1.1 Experimental Procedure .............. 436
12.6.2 Reverse Transition or Relaminarization ....... 436
12.6.2.1 Experimental Procedure ............. 437
12.7 Measurement in Boundary Layers ...................... 438
12.7.1 Laminar Boundary Layer on a Flat Plate ....... 438
12.7.2 Turbulent Boundary Layer on a Flat Plate ..... 440
12.8 Summary ............................................. 441
13 Data Acquisition and Processing ............................ 445
13.1 Introduction ........................................ 445
13.2 Data Acquisition Principle .......................... 445
13.2.1 Generation of Signal ......................... 446
13.2.2 Signal Conditioning .......................... 446
13.2.3 Multiplexing ................................. 447
13.2.3.1 Multichannel Analogue Multiplexed
System .............................. 448
13.2.3.2 Simultaneously Sampled Multiplexer
System .............................. 448
13.2.3.3 Multichannel Digital Multiplexer
System .............................. 448
13.2.3.4 Low-Level Multiplexing System ....... 449
13.3 Data Conversion ..................................... 450
13.3.1 Data Storage and Display ..................... 451
13.3.1.1 Data Processing ..................... 452
13.3.2 Digital Interfacing .......................... 452
13.4 Personal Computer Hardware .......................... 452
13.4.1 Central Processing Unit (CPU) ................ 453
13.4.1.1 Instruction Register and Decoder .... 453
13.4.1.2 Arithmetic Logic Unit (ALU) ......... 453
13.4.2 Input/Output Units ........................... 454
13.4.2.1 Input/Output Addressing ............. 455
13.4.2.2 System Buses ........................ 456
13.4.3 Input/Output Servicing ....................... 458
13.5 Data Acquisition Using Personal Computers ........... 459
13.5.1 The GPIB Interface ........................... 459
13.5.1.1 DT 2805 ADC/DAC Interface ........... 464
13.6 Digitization Errors Due to A/D Conversion ........... 465
13.7 Summary ............................................. 466
14 Uncertainty Analysis ....................................... 471
14.1 Introduction ........................................ 471
14.2 Estimation of Measurement Errors .................... 471
14.3 External Estimate of the Error ...................... 472
14.3.1 Dependence and Independence of Errors ........ 474
14.3.2 Estimation of External Error ................. 476
14.4 Internal Estimate of the Error ...................... 476
14.5 Uncertainty Analysis ................................ 477
14.5.1 Uses of Uncertainty Analysis ................. 477
14.6 Uncertainty Estimation .............................. 478
14.7 General Procedure ................................... 478
14.7.1 Uncertainty in Flow Mach Number .............. 479
14.8 Uncertainty Calculation ............................. 481
14.9 Summary ............................................. 482
References .................................................... 485
Index ......................................................... 487
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