Schlieren and Shadowgraph Techniques

1 Historical Background.- 1.1 The 17th Century.- 1.2 The 18th Century.- 1.3 The 19th Century.- 1.4 The 20th Century.- 2 Basic Concepts.- 2.1 Light Propagation Through Inhomogeneous Media.- 2.2 Definition of a Schliere.- 2.3 Distinction Between Schlieren and Shadowgraph Methods.- 2.4 Direct Shadowgraphy.- 2.5 Simple Lens-Type Schlieren System.- 2.6 On the Aspect of a Schlieren Image.- 3 Toepler's Schlieren Technique.- 3.1 Lens- and Mirror-Type Systems.- 3.2 Sensitivity.- 3.3 Measuring Range.- 3.4 Estimating the Sensitivity and Range Required.- 3.5 Resolving Power.- 3.6 Diffraction Effects.- 3.7 Magnification and Depth of Field.- 4 Large-Field and Focusing Schlieren Methods.- 4.1 Large Single- and Double-Mirror Systems.- 4.2 Traditional Schlieren Systems with Large Light Sources.- 4.3 Lens-and-Grid Techniques.- 4.4 Large-Field Scanning Schlieren Systems.- 4.5 Moiré-Fringe Methods.- 4.6 Holographic and Tomographic Schlieren.- 5 Specialized Schlieren Techniques.- 5.1 Special Schlieren CutoffsIll.- 5.1.1 Graded Filters.- 5.2 Color Schlieren Methods.- 5.3 Stereoscopic Schlieren.- 5.4 Schlieren Interferometry.- 5.5 Computer-Simulated Schlieren.- 5.6 Various Specialized Techniques.- 6 Shadowgraph Techniques.- 6.1 Background.- 6.2 Direct Shadowgraphy.- 6.3 “Focused” Shadowgraphy.- 6.4 Specialized Shadowgraph Techniques.- 7 Practical Issues.- 7.1 Optical Components.- 7.2 Equipment Fabrication, Alignment, and Operation.- 7.3 Capturing Schlieren Images and Shadowgrams.- 7.4 Commercial and Portable Schlieren Instruments.- 8 Setting Up Your Own Simple Schlieren and Shadowgraph System.- 8.1 Designing the Schlieren System.- 8.2 Determining the Cost.- 8.3 Choosing a Setup Location.- 8.4 Aligning the Optics.- 8.5 Troubleshooting.- 8.6 Recording the Schlieren Image or Shadowgram.-8.7 Conclusion.- 9 Applications.- 9.1 Phenomena in Solids.- 9.2 Phenomena in Liquids.- 9.3 Phenomena in Gases.- 9.4 Other Applications.- 10 Quantitative Evaluation.- 10.1 Quantitative Schlieren Evaluation by Photometry.- 10.2 Grid-Cutoff Methods.- 10.3 Quantitative Image Velocimetry.- 10.4 Quantitative Shadowgraphy.- 11 Summary and Outlook.- 11.1 Summary.- 11.2 Outlook: Issues for the Future.- 11.3 Closing Remarks.- References.- Appendix A Optical Fundamentals.- A. 1 Radiometry and Photometry.- A.2 Refraction Angle 8.- A.2.1 Small Optical Angles and Paraxial Space.- A.2.2 Huygens' Principle and Refraction.- A.3 Optical Components and Devices.- A.3.1 Conjugate Optical Planes.- A.3.2 Lensf/number.- A.3.3 The Thin-Lens Approximation.- A.3.4 Viewing Screens and Ground Glass.- A.3.5 Optical Density.- A.4 Optical Aberrations.- A.5 Light and the Human Eye.- A.6 Geometric Theory of Light Refraction by a Schliere.- Appendix B The Schlieren System as a Fourier Optical Processor.- B. 1 The Basic Fourier Processor with no Schlieren Present.- B.2 The Addition of a Schlieren Test Object.- B.3 The Schlieren Cutoff.- B.4 Other Spatial Filters.- B.5 Partially-Coherent and Polychromatic Illumination.- Appendix C Parts List for a Simple Schlieren/ Shadowgraph System.- C.l Optics.- C.2 Illumination.- C.3 Miscellaneous Components.- C.4 Optical Mounts.- Appendix D Suppliers of Schlieren Systems and Components.- D.l Complete Schlieren Systems.- D.2 Schlieren Field Mirrors.- D.3 Light Sources.- D.4 Components.- D.5 Focusing Schlieren Lenses.- D.6 Miscellaneous.- Color Plates.