Schlieren and Shadowgraph Techniques

by Settles, G. S.

• ISBN13: 9783540661559
• ISBN10: 3540661557
• Format: Hardcover
• Copyright: 2001-11-01
• Publisher: Springer Verlag

Summary

Schlieren and shadowgraph techniques are basic and valuable tools in various scientific and engineering disciplines. They allow us to see the invisible: the optical inhomogeneities in transparent media like air, water, and glass that otherwise cause only ghostly distortions of our normal vision. These techniques are discussed briefly in many books and papers, but there is no up-to-date complete treatment of the subject before now. The book is intended as a practical guide for those who want to use these methods, as well as a resource for a broad range of disciplines where scientific visualization is important. The colorful 400-year history of these methods is covered in an extensive introductory chapter accessible to all readers.

Table of Contents

List of Nomenclature	xv
Historical Background	1	(24)
The 17th Century	1	(3)
The 18th Century	4	(2)
The 19th Century	6	(9)
The 20th Century	15	(10)
Basic Concepts	25	(14)
Light Propagation Through Inhomogeneous Media	25	(3)
Definition of a Schliere	28	(1)
Distinction Between Schlieren and Shadowgraph Methods	29	(1)
Direct Shadowgraphy	30	(2)
Simple Lens-Type Schlieren System	32	(5)
Point Light Source	32	(2)
Extended Light Source	34	(3)
On the Aspect of a Schlieren Image	37	(2)
Toepler's Schlieren Technique	39	(38)
Lens- and Mirror-Type Systems	39	(9)
Lens Systems	40	(2)
Mirror Systems	42	(6)
Sensitivity	48	(12)
Definition and Geometrical Theory	48	(4)
Sensitivity Examples	52	(2)
The Limits of Sensitivity	54	(3)
Sensitivity Enhancement by Post-Processing	57	(3)
Measuring Range	60	(3)
Definition of Measuring Range	60	(1)
Adjustment of Measuring Range	61	(2)
Estimating the Sensitivity and Range Required	63	(2)
Resolving Power	65	(1)
Diffraction Effects	66	(7)
Diffraction Halos Due to Opaque Edges in the Test Area	66	(2)
Diffraction at the Knife-Edge	68	(5)
Magnification and Depth of Field	73	(4)
Image Magnification and the Focusing Lens	73	(1)
Depth of Field	74	(3)
Large-Field and Focusing Schlieren Methods	77	(34)
Large Single- and Double-Mirror Systems	77	(4)
Availability of Large Schlieren Mirrors	77	(1)
Examples of Large-Mirror Systems	78	(1)
Penn State's 1-Meter Coincident Schlieren System	79	(2)
Traditional Schlieren Systems with Large Light Sources	81	(3)
Lens-and-Grid Techniques	84	(20)
Simple Background Distortion	84	(2)
Background Grid Distortion	86	(1)
Large Colored Grid Background	87	(1)
The Modern Focusing/Large-Field Schlieren System	88	(10)
Penn State's Full-Scale Schlieren System	98	(6)
Large-Field Scanning Schlieren Systems	104	(4)
Scanning Schlieren Systems for Moving Objects	104	(2)
Schlieren Systems with Scanning Light Source and Cutoff	106	(2)
Moire-Fringe Methods	108	(1)
Holographic and Tomographic Schlieren	109	(2)
Specialized Schlieren Techniques	111	(32)
Special Schlieren Cutoffs	111	(11)
Graded Filters	112	(3)
Exponential Cutoffs and Source Filters	115	(1)
Matched Spatial Filters at Source and Cutoff	116	(3)
Phase Contrast	119	(2)
Photochromic and Photorefractive Cutoffs	121	(1)
Color Schlieren Methods	122	(8)
Reasons for Introducing Color	122	(1)
Conversion from Monochrome to Color Schlieren	123	(1)
Classification of Color Schlieren Techniques	123	(5)
Recent Developments	128	(2)
Stereoscopic Schlieren	130	(2)
Schlieren Interferometry	132	(4)
The Wollaston-Prism Shearing (Differential) Interferometer	132	(2)
Diffraction-Based Schlieren Interferometers	134	(2)
Computer-Simulated Schlieren	136	(1)
Various Specialized Techniques	137	(6)
Resonant Reactivity and the Visualization of Sound	138	(1)
Anamorphic Schlieren Systems	138	(1)
Schlieren Observation of Tracers	138	(2)
Two-View Schlieren	140	(1)
Immersion Methods	140	(1)
Infrared Schlieren	140	(3)
Shadowgraph Techniques	143	(22)
Background	143	(4)
Historical Development	143	(1)
The Role of Shadowgraphy	144	(1)
Advantages and Limitations	145	(2)
Direct Shadowgraphy	147	(8)
Direct Shadowgraphy in Diverging Light	148	(4)
Direct Shadowgraphy in Parallel Light	152	(3)
``Focused'' Shadowgraphy	155	(4)
Principle of Operation	155	(1)
History and Terminology	156	(1)
Advantages and Limitations	157	(1)
Magnification, Illuminance, and the Virtual Shadow Effect	158	(1)
``Focused'' Shadowgraphy in Ballistic Ranges	158	(1)
Specialized Shadowgraph Techniques	159	(6)
Large-Scale Shadowgraphy	159	(2)
Microscopic, Stereoscopic, and Holographic Shadowgraphy	161	(1)
Computed Shadowgraphy	162	(1)
Conical Shadowgraphy	162	(3)
Practical Issues	165	(36)
Optical Components	165	(11)
Light Sources	165	(5)
Mirrors	170	(1)
Schlieren Cutoffs and Source Filters	171	(1)
Condensers and Source Slits	172	(2)
The Required Optical Quality	174	(2)
Equipment Fabrication, Alignment, and Operation	176	(8)
Schlieren System Design Using Ray Tracing Codes	176	(1)
Fabrication of Apparatus	177	(1)
Setup, Alignment, and Adjustment	178	(3)
Vibration and Mechanical Stability	181	(2)
Stray Light, Self Luminous Events, and Secondary Images	183	(1)
Interference from Ambient Airflows	184	(1)
Capturing Schlieren Images and Shadowgrams	184	(11)
Photography and Cinematography	185	(3)
Videography	188	(1)
High-Speed imaging	189	(4)
Front-Lighting	193	(2)
Commercial and Portable Schlieren Instruments	195	(6)
Soviet Instruments	195	(3)
Western Instruments	198	(1)
Portable Schlieren Apparatus	198	(3)
Setting Up Your Own Simple Schlieren and Shadowgraph System	201	(10)
Designing the Schlieren System	201	(2)
Determining the Cost	203	(1)
Choosing a Setup Location	204	(1)
Aligning the Optics	205	(1)
Troubleshooting	206	(2)
Recording the Schlieren Image or Shadowgram	208	(1)
Conclusion	209	(2)
Applications	211	(52)
Phenomena in Solids	211	(4)
Glass Technology	211	(2)
Polymer-Film Characterization	213	(1)
Fracture Mechanics and Terminal Ballistics	214	(1)
Specular Reflection from Surfaces	215	(1)
Phenomena in Liquids	215	(6)
Convective Heat and Mass Transfer	215	(2)
Liquid Surface Waves	217	(2)
Liquid Atomization and Sprays	219	(1)
Ultrasonics	219	(1)
Water Tunnel Testing and Terminal Ballistics	220	(1)
Phenomena in Gases	221	(16)
Agricultural Airflows	221	(1)
Aero-Optics	222	(1)
Architectural Acoustics	223	(1)
Boundary Layers	224	(1)
Convective Heat and Mass Transfer	225	(1)
Heating, Ventilation, and Air-Conditioning	226	(2)
Gas Leak Detection	228	(1)
Electrical Breakdown and Discharge	229	(1)
Explosions, Blasts, Shock Waves, and Shock Tubes	230	(1)
Ballistics	231	(2)
Gas Dynamics and High-Speed Wind Tunnel Testing	233	(2)
Supersonic Jets and Jet Noise	235	(1)
Turbomachinery and Rotorcraft	236	(1)
Other Applications	237	(26)
Art and music	237	(3)
Biomedical Applications	240	(4)
Combustion	244	(1)
Geophysics	245	(1)
Industrial Applications	246	(1)
Materials Processing	247	(2)
Microscopy	249	(3)
Optical Processing	252	(1)
Optical Shop Testing	253	(1)
Outdoor Schlieren and Shadowgraphy	254	(5)
Plasma Dynamics	259	(1)
Television Light Valve Projection	260	(1)
Turbulence	261	(2)
Quantitative Evaluation	263	(16)
Quantitative Schlieren Evaluation by Photometry	264	(4)
Absolute Photometric Methods	265	(1)
Standard Photometric Methods	266	(2)
Grid-Cutoff Methods	268	(5)
Focal Grids	268	(3)
Defocused Grids	271	(1)
Defocused Filament Cutoff	272	(1)
Quantitative Image Velocimetry	273	(4)
Background	273	(1)
Multiple-Exposure Eddy and Shock Velocimetry	274	(1)
Schlieren Image Correlation Velocimetry	274	(1)
Focusing Schlieren Deflectometry	275	(1)
The Background-Oriented Schlieren System	276	(1)
Quantitative Shadowgraphy	277	(2)
Double Integration of ∂2n/∂y2	277	(1)
Turbulence Research	277	(1)
Shock-Wave Strength Quantitation	277	(1)
Grid Shadowgraphy Methods	277	(2)
Summary and Outlook	279	(12)
Summary	279	(5)
Perceptions Outside the Scientific Community	279	(1)
Other Lessons Learned	280	(1)
Further Comments on Historical Development	281	(1)
Further Comments on Images and Visualization	281	(2)
Renewed Vitality	283	(1)
Outlook: Issues for the Future	284	(5)
Predictions	284	(2)
Opportunities	286	(2)
Recommendations	288	(1)
Closing Remarks	289	(2)
References	291	(42)
Appendix A Optical Fundamentals	333	(8)
A.1 Radiometry and Photometry	333	(1)
A.2 Refraction Angle &epsis;	334	(1)
A.2.1 Small Optical Angles and Paraxial Space	334	(1)
A.2.2 Huygens' Principle and Refraction	334	(1)
A.3 Optical Components and Devices	335	(1)
A.3.1 Conjugate Optical Planes	335	(1)
A.3.2 Lens f/number	335	(1)
A.3.3 The Thin-Lens Approximation	335	(1)
A.3.4 Viewing Screens and Ground Glass	336	(1)
A.3.5 Optical Density	336	(1)
A.4 Optical Aberrations	336	(1)
A.5 Light and the Human Eye	337	(1)
A.6 Geometric Theory of Light Refraction by a Schliere	338	(3)
Appendix B The Schlieren System as a Fourier Optical Processor	341	(12)
B.1 The Basic Fourier Processor with no Schlieren Present	341	(3)
B.2 The Addition of a Schlieren Test Object	344	(1)
B.3 The Schlieren Cutoff	345	(2)
B.4 Other Spatial Filters	347	(3)
B.5 Partially-Coherent and Polychromatic Illumination	350	(3)
Appendix C Parts List for a Simple Schlieren/ Shadowgraph System	353	(2)
C.1 Optics	353	(1)
C.2 Illumination	354	(1)
C.3 Miscellaneous Components	354	(1)
C.4 Optical Mounts	354	(1)
Appendix D Suppliers of Schlieren Systems and Components	355	(6)
D.1 Complete Schlieren Systems	355	(1)
D.2 Schlieren Field Mirrors	356	(1)
D.3 Light Sources	357	(1)
D.4 Components	358	(1)
D.5 Focusing Schlieren Lenses	359	(1)
D.6 Miscellaneous	359	(2)
Index	361	(6)
Color Plates	367