PREFACE ......................................................... v
1 INTERPRETATION OF FLOW VISUALIZATION ......................... 1
1.1 Introduction ............................................ 1
1.2 Critical Points in Flow Patterns ........................ 1
1.3 Relationship between Streamlines, Pathlines and
Streaklines ............................................. 9
1.4 Sectional Streamlines .................................. 15
1.5 Bifurcation Lines ...................................... 16
1.6 Interpretation of Unsteady Flow Patterns with the Aid
of Streaklines and Streamlines ......................... 18
1.7 Concluding Remarks ..................................... 23
1.8 References ............................................. 24
2 HYDROGEN BUBBLE VISUALIZATION ............................... 27
2.1 Introduction ........................................... 27
2.2 The Hydrogen Bubble Generating System .................. 29
2.3 Bubble Probes .......................................... 32
2.4 Lighting ............................................... 36
2.5 Unique Applications .................................... 37
2.6 References ............................................. 41
3 DYE AND SMOKE VISUALIZATION ................................. 43
3.1 Introduction ........................................... 43
3.2 Flow Visualization in Water ............................ 44
3.2.1 Conventional dye ................................ 44
3.2.2 Laundry brightener .............................. 45
3.2.3 Milk ............................................ 45
3.2.4 Fluorescent dye ................................. 45
3.2.5 Methods of dye injection ........................ 46
3.2.6 Rheoscopic fluid ................................ 48
3.2.7 Electrolytic precipitation ...................... 49
3.3 Flow Visualization in Air .............................. 52
3.3.1 Smoke tunnel .................................... 52
3.3.2 Smoke generator ................................. 53
3.3.3 Smoke-wire technique ............................ 54
3.3.4 Titanium tetrachloride .......................... 57
3.4 Photographic Equipment and Techniques .................. 58
3.4.1 Lighting ........................................ 58
3.4.2 Camera .......................................... 61
3.4.3 Lens ............................................ 63
3.4.4 Film ............................................ 66
3.5 Cautionary Notes ....................................... 66
3.6 References ............................................. 69
4 MOLECULAR TAGGING VELOCIMETRY ............................... 73
4.1 Introduction ........................................... 73
4.2 Properties of Photo-Sensitive Tracers .................. 74
4.2.1 Photochromic dyes ............................... 74
4.2.2 Phosphorescent supramolecules ................... 74
4.2.3 Caged dyes ...................................... 76
4.3 Examples of Molecular Tagging Measurements ............. 80
4.3.1 Phosphorescent supramolecules ................... 80
4.3.2 Caged dye tracers ............................... 82
4.4 Image Processing and Experimental Accuracy ............. 86
4.4.1 Line processing techniques ...................... 86
4.4.2 Grid processing techniques ...................... 89
4.4.3 Ray tracing ..................................... 89
4.5 References ............................................. 90
5 PLANAR LASER IMAGING ........................................ 93
5.1 Introduction ........................................... 93
5.2 Planar Laser-Induced Fluorescence ...................... 95
5.3 Rayleigh Imaging from Molecules and Particles ......... 102
5.4 Filtered Rayleigh Scattering .......................... 105
5.5 Planar Doppler Velocimetry ............................ 111
5.6 Summary ............................................... 117
5.7 References ............................................ 118
6 DIGITAL PARTICLE IMAGE VELOCIMETRY ......................... 123
6.1 Quantitative Flow Visualization ....................... 123
6.2 DPIV Experimental Setup ............................... 124
6.3 Particle Image Velocimetry: A Visual Presentation ..... 125
6.4 Image Correlation ..................................... 126
6.4.1 Peak finding ................................... 129
6.4.2 Computational implementation of DPIV in
frequency space ................................ 130
6.5 Video Imaging ......................................... 130
6.6 Post Processing ....................................... 132
6.6.1 Outlier removal ................................ 132
6.6.2 Differentiable flow properties ................. 133
6.6.3 Integrable flow properties ..................... 135
6.7 Sources of Error ...................................... 135
6.7.1 Uncertainty due to particle image density ...... 136
6.7.2 Uncertainty due to velocity gradients within
the interro-gation Windows ..................... 136
6.7.3 Uncertainty due to different particle size
imaging ........................................ 137
6.7.4 Effects of using different size interrogation
Windows ........................................ 137
6.7.5 Mean-bias error removal ........................ 138
6.8 DPIV Applications ..................................... 141
6.8.1 Investigation of vortex ring formation ......... 141
6.8.2 A novel application for force prediction
DPIV ........................................... 141
6.8.3 DPIV and a CFD counterpart: a common ground .... 141
6.9 Conclusion ............................................ 143
6.10 References ............................................ 145
7 SURFACE TEMPERATURE SENSING WITH THERMO-CHROMIC LIQUID
CRYSTALS ................................................... 149
7.1 Introduction .......................................... 149
7.1.1 Calibration techniques ......................... 150
7.1.2 Convective heat transfer coefficient
measurement techniques ......................... 151
7.2 Implementation ........................................ 155
7.2.1 Sensing sheet preparation ...................... 155
7.2.2 Test surface illumination ...................... 156
7.2.3 Data reduction ................................. 157
7.2.4 Calibration .................................... 159
7.2.5 Establishing uncertainty ....................... 161
7.3 Examples .............................................. 161
7.3.1 Turbine cascade ................................ 161
7.3.2 Turbulent spot and boundary layer .............. 162
7.3.3 Turbulent juncture flow ........................ 163
7.4 Concluding Remarks .................................... 165
7.5 References ............................................ 166
8 PRESSURE AND SHEAR SENSITIVE COATINGS ...................... 169
8.1 Introduction .......................................... 169
8.2 Pressure-Sensitive Paint .............................. 170
8.2.1 Obtaining and applying pressure-sensitive
paint .......................................... 173
8.2.2 Lamps .......................................... 175
8.2.3 Cameras ........................................ 176
8.2.4 Data reduction ................................. 178
8.3 Shear-Sensitive Liquid Crystal Coating Method ......... 180
8.3.1 Color-change responses to shear ................ 181
8.3.2 Coating application ............................ 183
8.3.3 Lighting and imaging ........................... 184
8.3.4 Data acquisition and analysis .................. 185
8.3.5 Example: Visualization of transition and
Separation ..................................... 187
8.3.6 Example: Application of shear vector method .... 190
8.4 Fringe Imaging Skin Friction Interferometry ........... 192
8.4.1 Physical principles ............................ 192
8.4.2 Surface preparation ............................ 193
8.4.3 Lighting ....................................... 194
8.4.4 Imaging ........................................ 196
8.4.5 Calibration .................................... 197
8.4.6 Data reduction ................................. 197
8.4.7 Uncertainty .................................... 199
8.4.8 Examples ....................................... 200
8.5 References ............................................ 201
9 METHODS FOR COMPRESSIBLE FLOWS ............................. 205
9.1 Introduction .......................................... 205
9.2 Basic Optical Concepts ................................ 206
9.3 Index of Refraction for a Gas ......................... 209
9.4 Light Ray Deflection and Retardation in a Refractive
Field ................................................. 211
9.5 Shadowgraph ........................................... 213
9.6 Schlieren Method ...................................... 219
9.7 Interferometry ........................................ 221
9.8 Interference .......................................... 224
9.9 Mach-Zehnder Interferometer ........................... 226
9.10 Holography ............................................ 230
9.11 Holographic Interferometry ............................ 232
9.12 Applications .......................................... 237
9.13 Summary ............................................... 240
9.14 References ............................................ 242
10 THREE-DIMENSIONAL IMAGING .................................. 245
10.1 Introduction .......................................... 245
10.2 3-D Imaging Techniques ................................ 245
10.3 Image Data Types ...................................... 249
10.4 Laser Scanner Designs ................................. 250
10.5 Discrete Laser Sheet Systems .......................... 251
10.6 Double Scan Laser Sweep Systems ....................... 252
10.7 Single Scan Laser Sweep Systems (Discrete) ............ 256
10.8 Drum Scanners ......................................... 258
10.9 Multiple Fixed Laser Sheets ........................... 260
10.10 Moving Laser Sheet Systems ........................... 262
10.11 Imaging Issues and Trade-OfTs ........................ 263
10.11.1 Position aecuraey of laser sheets ............. 263
10.11.2 Illumination issues ........................... 264
10.11.3 Sweeps versus sheets for CW lasers ............ 265
10.11.4 Optical components ............................ 267
10.11.5 Methods of control ............................ 268
10.11.6 Operational considerations .................... 269
10.11.7 Imaging devices ............................... 272
10.12 Detailed Example ..................................... 273
10.12.1 Control system design ......................... 276
10.13 Analysis and Display of Data ......................... 279
10.13.1 Processing and analysis of data ............... 279
10.13.2 Methods of presentation and display ........... 280
10.14 Concluding remarks ................................... 283
10.15 Acknowledgments ...................................... 283
10.16 References ........................................... 284
11 QUANTITATIVE FLOW VISUALIZATION VIA FULLY-RESOLVED
FOUR-DIMENSIONAL IMAGING ................................... 289
11.1 Introduction .......................................... 289
11.2 Technical Considerations .............................. 291
11.2.1 Laser induced fluorescence ..................... 291
11.2.2 Beam scanning electronics ...................... 291
11.2.3 Data acquisition System ........................ 294
11.2.4 Signal levels .................................. 295
11.2.5 Signal-to-noise ratio .......................... 300
11.2.6 Spatial and temporal resolution ................ 302
11.2.7 Data processing ................................ 306
11.3 Sample Applications ................................... 308
11.3.1 Fine structure of turbulent scalar fields ...... 308
11.3.2 Assessment of Taylor's hypothesis .............. 310
11.3.3 Scalar imaging velocimetry ..................... 311
11.3.4 Fractal scaling of turbulent scalar fields ..... 311
11.4 Further Information ................................... 313
11.5 References ............................................ 315
12 VISUALIZATION, FEATURE EXTRACTION AND QUAN-TIFICATION OF
NUMERICAL VISUALIZATIONS OF HIGH GRADIENT COMPRESSIBLE
FLOWS ...................................................... 317
12.1 Introduction .......................................... 317
12.1.1 Fundamental configuration ...................... 318
12.2 Visualization Techniques ............................. 321
12.2.1 Numerical analog of experimental techniques .... 321
12.2.2 Smoothing and noise suppression ................ 325
12.2.3 Selection of variables for visualization ....... 325
12.3 Quantification of Shocks and Contacts ................. 327
12.3.1 One-dimensional example ........................ 328
12.3.2 Algorithm ...................................... 328
12.3.3 Two-dimensional example ........................ 333
12.3.4 Contact tracking and convergence of
simulations .................................... 334
12.3.5 Quantification of local shock properties ....... 337
12.4 Conclusion ............................................ 339
12.5 References ............................................ 343
COLOR PLATES AND FLOW GALLERY ................................. 345
|
