An algebraic turbulence model for two- and three-dimensional separated flows is specified that avoids the necessity for finding the edge of the boundary layer. Properties of the model are determined and comparisons made with experiment for an incident shock on a flat plate, separated flow over a compression corner, and transonic flow over an airfoil. Separation and reattachment points from numerical Navier-Stokes solutions agree with experiment within one boundary-layer thickness. Use of law-of-the-wall boundary conditions does not alter the predictions significantly. Applications of the model to other cases are contained in companion papers.

Thin-layer approximation and algebraic model for separated turbulent flows

Thermophysical Properties Research Literature Retrieval Guide Edited by Y. S. Touloukian, J. K. Gerritsen and N. Y. Moore Second edition, revised and expanded. Book 1: Pp. xxi + 819. Book 2: Pp.621. Book 3: Pp. ix + 1315. (New York: Plenum Press, 1967.) n.p.

/pdf/heat-and-mass-transfer-1yaijfx8vp.pdf

Heat and Mass Transfer

This paper describes the principles of a novel 3D PIV system based on the illumination, recording and reconstruction of tracer particles within a 3D measurement volume The technique makes use of several simultaneous views of the illuminated particles and their 3D reconstruction as a light intensity distribution by means of optical tomography The technique is therefore referred to as tomographic particle image velocimetry (tomographic-PIV) The reconstruction is performed with the MART algorithm, yielding a 3D array of light intensity discretized over voxels The reconstructed tomogram pair is then analyzed by means of 3D cross-correlation with an iterative multigrid volume deformation technique, returning the three-component velocity vector distribution over the measurement volume The principles and details of the tomographic algorithm are discussed and a parametric study is carried out by means of a computer-simulated tomographic-PIV procedure The study focuses on the accuracy of the light intensity field reconstruction process The simulation also identifies the most important parameters governing the experimental method and the tomographic algorithm parameters, showing their effect on the reconstruction accuracy A computer simulated experiment of a 3D particle motion field describing a vortex ring demonstrates the capability and potential of the proposed system with four cameras The capability of the technique in real experimental conditions is assessed with the measurement of the turbulent flow in the near wake of a circular cylinder at Reynolds 2,700

Tomographic particle image velocimetry

Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies.

https://iopscience.iop.org/article/10.1088/0034-4885/70/8/R02/pdf

Imaging with terahertz radiation

https://www.southampton.ac.uk/~nwb/lectures/GoodPracticeCFD/Articles/Validation_SAND2002-0529.pdf

Verification and Validation in Computational Fluid Dynamics

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.- 2.5.1 Point Light Source.- 2.5.2 Extended Light Source.- 2.6 On the Aspect of a Schlieren Image.- 3 Toepler's Schlieren Technique.- 3.1 Lens- and Mirror-Type Systems.- 3.1.1 Lens Systems.- 3.1.2 Mirror Systems.- 3.2 Sensitivity.- 3.2.1 Definition and Geometrical Theory.- 3.2.2 Sensitivity Examples.- 3.2.3 The Limits of Sensitivity.- 3.2.4 Sensitivity Enhancement by Post-Processing.- 3.3 Measuring Range.- 3.3.1 Definition of Measuring Range.- 3.3.2 Adjustment of Measuring Range.- 3.4 Estimating the Sensitivity and Range Required.- 3.5 Resolving Power.- 3.6 Diffraction Effects.- 3.6.1 Diffraction Halos Due to Opaque Edges in the Test Area.- 3.6.2 Diffraction at the Knife-Edge.- 3.7 Magnification and Depth of Field.- 3.7.1 Image Magnification and the Focusing Lens.- 3.7.2 Depth of Field.- 4 Large-Field and Focusing Schlieren Methods.- 4.1 Large Single- and Double-Mirror Systems.- 4.1.1 Availability of Large Schlieren Mirrors.- 4.1.2 Examples of Large-Mirror Systems.- 4.1.3 Perm State's 1-Meter Coincident Schlieren System.- 4.2 Traditional Schlieren Systems with Large Light Sources.- 4.3 Lens-and-Grid Techniques.- 4.3.1 Simple Background Distortion.- 4.3.2 Background Grid Distortion.- 4.3.3 Large Colored Grid Background.- 4.3.4 The Modern Focusing/Large-Field Schlieren System.- 4.3.5 Penn State's Full-Scale Schlieren System.- 4.4 Large-Field Scanning Schlieren Systems.- 4.4.1 Scanning Schlieren Systems for Moving Objects.- 4.4.2 Schlieren Systems with Scanning Light Source and Cutoff.- 4.5 Moire-Fringe Methods.- 4.6 Holographic and Tomographic Schlieren.- 5 Specialized Schlieren Techniques.- 5.1 Special Schlieren CutoffsIll.- 5.1.1 Graded Filters.- 5.1.2 Exponential Cutoffs and Source Filters.- 5.1.3 Matched Spatial Filters at Source and Cutoff.- 5.1.4 Phase Contrast.- 5.1.5 Photochromic and Photorefractive Cutoffs.- 5.2 Color Schlieren Methods.- 5.2.1 Reasons for Introducing Color.- 5.2.2 Conversion from Monochrome to Color Schlieren.- 5.2.3 Classification of Color Schlieren Techniques.- 5.2.4 Recent Developments.- 5.3 Stereoscopic Schlieren.- 5.4 Schlieren Interferometry.- 5.4.1 The Wollaston-Prism Shearing (Differential) Interferometer.- 5.4.2 Diffraction-Based Schlieren Interferometers.- 5.5 Computer-Simulated Schlieren.- 5.6 Various Specialized Techniques.- 5.6.1 Resonant Refractivity and the Visualization of Sound.- 5.6.2 Anamorphic Schlieren Systems.- 5.6.3 Schlieren Observation of Tracers.- 5.6.4 Two-View Schlieren.- 5.6.5 Immersion Methods.- 5.6.6 Infrared Schlieren.- 6 Shadowgraph Techniques.- 6.1 Background.- 6.1.1 Historical Development.- 6.1.2 The Role of Shadowgraphy.- 6.1.3 Advantages and Limitations.- 6.2 Direct Shadowgraphy.- 6.2.1 Direct Shadowgraphy in Diverging Light.- 6.2.2 Direct Shadowgraphy in Parallel Light.- 6.3 "Focused" Shadowgraphy.- 6.3.1 Principle of Operation.- 6.3.2 History and Terminology.- 6.3.3 Advantages and Limitations.- 6.3.4 Magnification, Illuminance, and the Virtual Shadow Effect.- 6.3.5 "Focused" Shadowgraphy in Ballistic Ranges.- 6.4 Specialized Shadowgraph Techniques.- 6.4.1 Large-Scale Shadowgraphy.- 6.4.2 Microscopic, Stereoscopic, and Holographic Shadowgraphy.- 6.4.3 Computed Shadowgraphy.- 6.4.4 Conical Shadowgraphy.- 7 Practical Issues.- 7.1 Optical Components.- 7.1.1 Light Sources.- 7.1.2 Mirrors.- 7.1.3 Schlieren Cutoffs and Source Filters.- 7.1.4 Condensers and Source Slits.- 7.1.5 The Required Optical Quality.- 7.2 Equipment Fabrication, Alignment, and Operation.- 7.2.1 Schlieren System Design Using Ray Tracing Codes.- 7.2.2 Fabrication of Apparatus.- 7.2.3 Setup, Alignment, and Adjustment.- 7.2.4 Vibration and Mechanical Stability.- 7.2.5 Stray Light, Self-Luminous Events, and Secondary Images.- 7.2.6 Interference from Ambient Airflows.- 7.3 Capturing Schlieren Images and Shadowgrams.- 7.3.1 Photography and Cinematography.- 7.3.2 Videography.- 7.3.3 High-Speed imaging.- 7.3.4 Front-Lighting.- 7.4 Commercial and Portable Schlieren Instruments.- 7.4.1 Soviet Instruments.- 7.4.2 Western Instruments.- 7.4.3 Portable Schlieren Apparatus.- 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.- 9.1.1 Glass Technology.- 9.1.2 Polymer-Film Characterization.- 9.1.3 Fracture Mechanics and Terminal Ballistics.- 9.1.4 Specular Reflection from Surfaces.- 9.2 Phenomena in Liquids.- 9.2.1 Convective Heat and Mass Transfer.- 9.2.2 Liquid Surface Waves.- 9.2.3 Liquid Atomization and Sprays.- 9.2.4 Ultrasonics.- 9.2.5 Water Tunnel Testing and Terminal Ballistics.- 9.3 Phenomena in Gases.- 9.3.1 Agricultural Airflows.- 9.3.2 Aero-Optics.- 9.3.3 Architectural Acoustics.- 9.3.4 Boundary Layers.- 9.3.5 Convective Heat and Mass Transfer.- 9.3.6 Heating, Ventilation, and Air-Conditioning.- 9.3.7 Gas Leak Detection.- 9.3.8 Electrical Breakdown and Discharge.- 9.3.9 Explosions, Blasts, Shock Waves, and Shock Tubes.- 9.3.10 Ballistics.- 9.3.11 Gas Dynamics and High-Speed Wind Tunnel Testing.- 9.3.12 Supersonic Jets and Jet Noise.- 9.3.13 Turbomachinery and Rotorcraft.- 9.4 Other Applications.- 9.4.1 Art and music.- 9.4.2 Biomedical Applications.- 9.4.3 Combustion.- 9.4.4 Geophysics.- 9.4.5 Industrial Applications.- 9.4.6 Materials Processing.- 9.4.7 Microscopy.- 9.4.8 Optical Processing.- 9.4.9 Optical Shop Testing.- 9.4.10 Outdoor Schlieren and Shadowgraphy.- 9.4.11 Plasma Dynamics.- 9.4.12 Television Light Valve Projection.- 9.4.13 Turbulence.- 10 Quantitative Evaluation.- 10.1 Quantitative Schlieren Evaluation by Photometry.- 10.1.1 Absolute Photometric Methods.- 10.1.2 Standard Photometric Methods.- 10.2 Grid-Cutoff Methods.- 10.2.1 Focal Grids.- 10.2.2 Defocused Grids.- 10.2.3 Defocused Filament Cutoff.- 10.3 Quantitative Image Velocimetry.- 10.3.1 Background.- 10.3.2 Multiple-Exposure Eddy and Shock Velocimetry.- 10.3.3 Schlieren Image Correlation Velocimetry.- 10.3.4 Focusing Schlieren Deflectometry.- 10.3.5 The Background-Oriented Schlieren System.- 10.4 Quantitative Shadowgraphy.- 10.4.1 Double Integration of d2n/ dy2.- 10.4.2 Turbulence Research.- 10.4.3 Shock-Wave Strength Quantitation.- 10.4.4 Grid Shadowgraphy Methods.- 11 Summary and Outlook.- 11.1 Summary.- 11.1.1 Perceptions Outside the Scientific Community.- 11.1.2 Other Lessons Learned.- 11.1.3 Further Comments on Historical Development.- 11.1.4 Further Comments on Images and Visualization.- 11.1.5 Renewed Vitality.- 11.2 Outlook: Issues for the Future.- 11.2.1 Predictions.- 11.2.2 Opportunities.- 11.2.3 Recommendations.- 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.

Schlieren and Shadowgraph Techniques : Visualizing Phenomena in Transparent Media

a review of recent developments in schlieren and schlieren visualization joseph shepherd lecture # 09: flow visualization techniques: schlieren and shadowgraph, schlieren and interferometry part 01 schlieren and shadowgraph techniques osfp schlieren and shadowgraph techniques module 5: schlieren and shadowgraph lecture 26 shadowgraph and schlieren techniques schlieren techniques for the visualization of current visualization based on refractive-index affects shadowgraph and schlieren techniques towards a schlieren camera northwestern university schlieren photography principles rit scholar works introduction to shadowgraph and schlieren imaging chapter 2 laser schlieren and shadowgraph springer background oriented schlieren applied to study shock mae 123 : mechanical engineering laboratory ii -fluids recent developments in schlieren and shadowgraphy schlieren and shadowgraph techniques: visualizing optical considerationsand limitations of the schlieren method principles and techniques of schlieren imaging systems mice a simple classroom demonstration of natural convection module 5: schlieren and shadowgraph lecture 27: schlieren retroreflective shadowgraph technique for large-scale flow optical methods for visualization of ultrasound fields schlieren & shadowgraph techniques steps forward physically-based interactive schlieren flow visualization schlieren and shadowgraph techniques pdf download shadow, schlieren and color interferometry physically-based interactive flow visualization based on schlieren & shadowgraph techniques steps forward background oriented schlieren (bos) and other flow size 50,24mb doc book schlieren and shadowgraph techniques 6 shadowgraph techniques springer pradipta kumar panigrahi krishnamurthy muralidhar schlieren and shadowgraph techniques jlip application of the shadowgraph flow visualization shadowgraph, schlieren and interferometry in a 2d a fluid motion estimator for schlieren image velocimetry schlieren and shadowgraph techniques springer shadowgraph, schlieren and interferometry in a 2d quantitative fourier analysis of schlieren masks: the schlieren, shadowgraph and direct photography fkm.utm schlieren and shadowgraph techniques for °uid physics four decades of utilizing shadowgraph techniques to study color schlieren imaging with a two-path, double knife edge schlieren and shadowgraph techniques gerrymarshall free download schlieren & shadowgraph techniques book shadow-schlieren-book-1 rit people

https://www.springer.com/cda/content/document/productFlyer/productFlyer_978-3-540-66155-9.pdf?SGWID=0-0-1297-1447935-0

Schlieren and shadowgraph techniques

An experimental study has been carried out to detail the interaction of a compressible turbulent boundary layer with shock waves of varying strengths. The interaction was produced by two-dimension al compression corners of 8, 16, 20, and 24 deg angles. The incoming boundary layer had an edge Mach number of 2.85 and a Reynolds number of 1.7 million based on overall thickness. Detailed mean flow and surface measurements are presented for the four corner angles. The 8 deg corner flow was found to be fully attached, while the 16 deg case was near incipient separation. Both the 20 and 24 deg corners produced significant flow separation regions. In the discussion of these results, emphasis is placed on the development of flowfield properties from attached to separated conditions. Comparisons made with a computational solution of the Navier-Stokes equations show good agreement when the corner flow is not separated. Separated corner flows seem to require a more complex turbulence model in the computational solution.

Detailed Study of Attached and Separated Compression Corner Flowfields in High Reynolds Number Supersonic Flow

Whether mammalian scent-tracking is aided by inter-nostril comparisons is unknown. We assessed this in humans and found that (i) humans can scent-track, (ii) they improve with practice, (iii) the human nostrils sample spatially distinct regions separated by approximately 3.5 cm and, critically, (iv) scent-tracking is aided by inter-nostril comparisons. These findings reveal fundamental mechanisms of scent-tracking and suggest that the poor reputation of human olfaction may reflect, in part, behavioral demands rather than ultimate abilities.

Mechanisms of scent-tracking in humans

Various infectious agents are known to be transmitted naturally via respiratory aerosols produced by infected patients. Such aerosols may be produced during normal activities by breathing, talking, coughing and sneezing. The schlieren optical method, previously applied mostly in engineering and physics, can be effectively used here to visualize airflows around human subjects in such indoor situations, non-intrusively and without the need for either tracer gas or airborne particles. It accomplishes this by rendering visible the optical phase gradients owing to real-time changes in air temperature. In this study, schlieren video records are obtained of human volunteers coughing with and without wearing standard surgical and N95 masks. The object is to characterize the exhaled airflows and evaluate the effect of these commonly used masks on the fluid-dynamic mechanisms that spread infection by coughing. Further, a high-speed schlieren video of a single cough is analysed by a computerized method of tracking individual turbulent eddies, demonstrating the non-intrusive velocimetry of the expelled airflow. Results show that human coughing projects a rapid turbulent jet into the surrounding air, but that wearing a surgical or N95 mask thwarts this natural mechanism of transmitting airborne infection, either by blocking the formation of the jet (N95 mask), or by redirecting it in a less harmful direction (surgical mask).

Gary S. Settles

Papers

Schlieren and Shadowgraph Techniques : Visualizing Phenomena in Transparent Media

Schlieren and shadowgraph techniques

Detailed Study of Attached and Separated Compression Corner Flowfields in High Reynolds Number Supersonic Flow

Mechanisms of scent-tracking in humans

A schlieren optical study of the human cough with and without wearing masks for aerosol infection control.