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Journal articles on the topic 'Shadowgraph'

Author: Grafiati

Published: 4 June 2021

Last updated: 10 March 2023

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1

Smith, Cary, Mark Gragston, Yue Wu, and Zhili Zhang. "Experimental Characterization of Two-Phase Aerated Liquid Ethanol and Jet A Spray Flames." Applied Sciences 10, no. 19 (October 4, 2020): 6950. http://dx.doi.org/10.3390/app10196950.

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This work provides an analysis of an air-assisted atomizing nebulizer’s spray characteristics and combustion behaviors via application of various diagnostics. Two-phase far-field flows and flames of liquid ethanol and practical aviation fuel Jet A were characterized for the droplet distributions, fuel concentrations, and flame dynamics by shadowgraph, Mie scattering, and chemiluminescence imaging of CH*, C2*, and CO2*. Both instantaneous and time-averaged measurements of the two-phase flow and flame characteristics were obtained. Shadowgraphs were used to measure the probability distribution of the droplet diameters. Mie scattering was used to map fuel concentration and obtain the liquid spray cone angles. Estimates of the lifted flame height were obtained by both shadowgraph and Mie scattering, which were verified by the chemiluminescence images. The effect of flow rates on parameters such as flow characteristic, spray cone angle, and drop size spectrum were quantitatively characterized for both ethanol and practical aviation fuel Jet A.

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2

Corbett, J., C. L. S. Lewis, E. Robertson, S. Saadat, P. F. Cunningham, A. Cole, E. Trucu, M. H. Key, and S. J. Rose. "Recent experiments at the Rutherford Appleton Laboratory to study the laser driven compression of CH shell targets and the effects of increasing aspect ratio." Laser and Particle Beams 4, no. 3-4 (August 1986): 573–76. http://dx.doi.org/10.1017/s0263034600002251.

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Recent experiments to study the laser driven compression of CH shell targets and the effects of increasing aspect ratio using x-ray shadowgraph techniques are described. This work has been carried out at the Rutherford Appleton Laboratory's Central Laser Facility with 12 beam, 0·53 μm, 1·0 ns irradiation. X-ray shadowgraphy techniques have been used with a frame time of ∼100ps and spatial resolution of 5 to lOμm to obtain density profiles for the compressed targets. A systematic study of 150–200 μm targets with aspect ratios from ∼7 to ∼20 has been performed. The x-ray shadowgraphy techniques used are described, results in the form of x-radiographs presented and a discussion of preliminary results given.

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3

Greer, Adam T. "In-Situ Shadowgraph Imaging." Marine Technology Society Journal 52, no. 6 (November 1, 2018): 62–65. http://dx.doi.org/10.4031/mtsj.52.6.5.

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AbstractVarious imaging systems are producing complex data that improve our understanding of physical and biological coupling in the ocean. In-situ shadowgraph imaging is one sampling technique that captures detailed biological information for a wide range of plankton with differing body compositions (e.g., gelatinous to crustacean) in their natural orientations, as well as small-scale physical changes. When combined with rapidly advancing computer vision methods and high-resolution oceanographic observations, shadowgraph imagery holds promise for generating new discoveries in ocean science that are only limited by our creativity in asking new questions.

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4

Mursenkova, I., M. Timokhin, M. Tikhonov, A. Militsina, and A. Kuznetsov. "Digital processing of shadowgraph images taking into account the diffraction of light at a shock front." Journal of Physics: Conference Series 2127, no. 1 (November 1, 2021): 012001. http://dx.doi.org/10.1088/1742-6596/2127/1/012001.

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Abstract The aim of the study is to determine the shock wave position in experimental shadowgraph images and to evaluate the accuracy by digital image processing. The experimental images were obtained with the shock tube with a rectangular channel. The shadowgraph optical system formed a parallel light beam. It passed through the plane-parallel quartz glasses of the shock tube test section. The process synchronization system at the facility allows registering the shadowgraph images of unsteady flows with shock waves with a high-speed camera or with a single frame camera. The obtained spatial intensity profiles were used to determine the coordinates of gas-dynamic discontinuities at different stages of the flow evolution. shadowgraph patterns were analysed taking into account diffraction at the shock front in case of a laser light source.

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5

Phung, Van Duoc. "DEVELOPING A SHADOWGRAPH EXPERIMENT SYSTEM FOR CHARACTERIZING SPRAY ATOMIZATION." Journal of Science and Technique 17, no. 4 (September 27, 2022): 22–31. http://dx.doi.org/10.56651/lqdtu.jst.v17.n04.40110.56651/lqdtu.jst.v17.n04.401.

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The development of modern imaging techniques plays an imporatnt role in studying fuel spray atomization. Shadowgraph combines camera, lens and lightsources to experimentally determine micro parametters (droplet size, droplet size distribution, velocity of droplets) and macro parametters (cone angle, breakup length, penetration) of spray structure. To achieve high quality, shadowgraph systems need to be carefully validated to ensure realiability and capability of working under various operating conditions. This articledevelops an experiment system for characterizing spray atomization by shadowgraph imaging technique. A peliminary study on an air-blast atomizer is also provided.

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6

Phung, Van Duoc. "DEVELOPING A SHADOWGRAPH EXPERIMENT SYSTEM FOR CHARACTERIZING SPRAY ATOMIZATION." Journal of Science and Technique 17, no. 4 (September 27, 2022): 22–31. http://dx.doi.org/10.56651/lqdtu.jst.v17.n04.401.

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The development of modern imaging techniques plays an imporatnt role in studying fuel spray atomization. Shadowgraph combines camera, lens and lightsources to experimentally determine micro parametters (droplet size, droplet size distribution, velocity of droplets) and macro parametters (cone angle, breakup length, penetration) of spray structure. To achieve high quality, shadowgraph systems need to be carefully validated to ensure realiability and capability of working under various operating conditions. This articledevelops an experiment system for characterizing spray atomization by shadowgraph imaging technique. A peliminary study on an air-blast atomizer is also provided.

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7

Liu, Minghui, and John R. de Bruyn. "Traveling-wave convection in a narrow rectangular cell." Canadian Journal of Physics 70, no. 9 (September 1, 1992): 689–95. http://dx.doi.org/10.1139/p92-111.

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Traveling-wave convection in an ethanol–water mixture confined in a narrow rectangular cell of height:width aspect ratio 1:0.3 is studied using shadowgraph flow visualization. We are able to identify qualitatively the contributions to the shadowgraph intensity due to the concentration field in the convecting mixture. The measured shadowgraph intensities and traveling-wave frequencies share features with the results of numerical calculations, which assume an infinitely wide cell, and of experiments done in wider cells, but there are significant quantitative differences, apparently due to our highly constrained geometry.

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8

Linehan, Kelly A., and John R. de Bruyn. "Gravity currents and the electrolyte concentration field in electrochemical deposition." Canadian Journal of Physics 73, no. 3-4 (March 1, 1995): 177–86. http://dx.doi.org/10.1139/p95-025.

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Using shadowgraphs, we visualize local electrolyte concentration variations in quasi-two-dimensional electrochemical deposition experiments. Experiments have been performed in both circular and parallel-electrode geometries. Our results indicate that a region of ion depletion moves from the cathode towards the anode, while a region of enhanced concentration grows in from the anode. Large-scale gravity-driven flows, which drive the growth of these regions, are observed. The growth speed of the metal aggregate at the cathode is the same as the speed at which these flows move anions away from the cathode, except at the earliest stages of growth. By integrating the shadowgraph intensity, we calculate the concentration field in the parallel geometry.

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9

Watanabe, Ryuta, Takayuki Kikuchi, Takayuki Yamagata, and Nobuyuki Fujisawa. "Shadowgraph Imaging of Cavitating Jet." Journal of Flow Control, Measurement & Visualization 03, no. 03 (2015): 106–10. http://dx.doi.org/10.4236/jfcmv.2015.33010.

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10

Settles, Gary S. "Smartphone schlieren and shadowgraph imaging." Optics and Lasers in Engineering 104 (May 2018): 9–21. http://dx.doi.org/10.1016/j.optlaseng.2017.07.002.

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11

Wang, Fang, Zong Wei Yang, De Ren Kong, and Yun Fei Jia. "Research on the High-Speed Object Shadowgraph Image Processing Method Based on Adaptive Threshold Segmentation." Applied Mechanics and Materials 325-326 (June 2013): 1571–75. http://dx.doi.org/10.4028/www.scientific.net/amm.325-326.1571.

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Shadowgraph is an important method to obtain the flight characteristics of high-speed object, such as attitude and speed etc. To get the contour information of objects and coordinates of feature points from shadowgraph are the precondition of characteristics analysis. Current digital shadowgraph system composed of CCD camera and pulsed laser source is widely used, but still lack of the corresponding method in image processing. Therefore, the selection of an effective processing method in order to ensure high effectiveness and accuracy of image data interpretation is an urgent need to be solved. According to the features of shadowgraph, a processing method to realize the contour extraction of high-speed object by adaptive threshold segmentation is proposed based on median filtering in this paper, and verified with the OpenCV in VC environment, the identification process of the feature points are recognized. The result indicates that by using this method, contours of high-speed objects can be detected nicely, to combine relevant algorithm, the pixel coordinates of feature points such as the center of mass can be recognized accurately.

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12

Parsinejad, Farzan, Matyas Matlo, and Mohamad Metghalchi. "A Mathematical Model for Schlieren and Shadowgraph Images of Transient Expanding Spherical Thin Flames." Journal of Engineering for Gas Turbines and Power 126, no. 2 (April 1, 2004): 241–47. http://dx.doi.org/10.1115/1.1688368.

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Optical behavior of spherical flames is investigated using both Schlieren and shadowgraph methods. A mathematical model has been developed to predict the intensity of refracted light beams interacting with a transient expanding thin flame. Experimental facilities have been built to visualize transient expanding spherical flames. The facilities include a cylindrical chamber with two end glasses for optical observation. Shadowgraph and Schlieren pictures of flame propagation have been taken using a high-speed charged coupled device camera. Experimental results are in very good agreement with those predicted by the theoretical model. Schlieren and shadowgraph techniques have also been used to view smooth, cracked and cellular flames; these techniques will be useful in future in studies to determine the stability of propagating flame.

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13

Brassington, G. B., John C. Patterson, and M. Lee. "ANALYZING SHADOWGRAPH IMAGES: A NEW ALGORITHM." Journal of Flow Visualization and Image Processing 24, no. 1-4 (2017): 319–45. http://dx.doi.org/10.1615/jflowvisimageproc.v24.i1-4.180.

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14

Gearhart, Bradley, and Dan MacIsaac. "A Practical Classroom iPad Shadowgraph System." Physics Teacher 58, no. 1 (January 2020): 8–11. http://dx.doi.org/10.1119/1.5141961.

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15

Trainoff, Steven P., and David S. Cannell. "Physical optics treatment of the shadowgraph." Physics of Fluids 14, no. 4 (April 2002): 1340–63. http://dx.doi.org/10.1063/1.1449892.

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16

Rasenat, S., G. Hartung, B. L. Winkler, and I. Rehberg. "The shadowgraph method in convection experiments." Experiments in Fluids 7, no. 6 (June 1989): 412–20. http://dx.doi.org/10.1007/bf00193424.

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17

Uscinski, B. J., and B. Pruin. "A shadowgraph method for ocean acoustics." Waves in Random Media 9, no. 4 (October 1999): R1—R24. http://dx.doi.org/10.1088/0959-7174/9/4/201.

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18

Patterson, John C., G. B. Brassington, and M. Lee. "A NEW ALGORITHM FOR ANALYZING SHADOWGRAPH IMAGES." Journal of Flow Visualization and Image Processing 9, no. 1 (2002): 27. http://dx.doi.org/10.1615/jflowvisimageproc.v9.i1.30.

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19

Richter, H., S. Rasenat, and I. Rehberg. "The shadowgraph method at the Fréedericksz transition." Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals 222, no. 1 (January 1992): 219–28. http://dx.doi.org/10.1080/15421409208048696.

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20

WILLERT, CHRISTIAN E., and MORTEZA GHARIB. "The interaction of spatially modulated vortex pairs with free surfaces." Journal of Fluid Mechanics 345 (August 25, 1997): 227–50. http://dx.doi.org/10.1017/s0022112097006265.

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Spatially modulated vortex pairs were generated below a free surface by two counter-rotating flaps whose edges approximate a sinusoid. The surface interactions of the vertically approaching vortex pairs were visualized by the shadowgraph technique. Two limiting cases were investigated in detail: the interaction with a surfactant-rich (contaminated) surface and with a surfactant-poor (‘clean’) surface. In the latter case shadowgraph images showed that the underlying vortex core formed a line of circular surface depressions. Subsequent measurements of the temporally evolving velocity fields using digital particle image velocimetry (DPIV) of the vortex pair cross-sections and the subsurface plane confirmed the connection process of the main vortex core with the surface. As a result of the connection the initially modulated vortex tube was broken into a line of U-vortices. In the presence of surfactants this connection could not be observed; rather a Reynolds ridge (or stagnation line) was formed and a very weak connection of the secondary separation vortex could be seen in the shadowgraphs as well as measured with the time-resolved DPIV technique.A prerequisite for connection of the vortex with the surface is that the flow's kinematics force the vortex core, that is, regions of concentrated vorticity, toward the surface. The ensuing locally concentrated viscous flux of surface-parallel vorticity through the surface is balanced by a local surface deceleration. Surface-normal vorticity appears on each side of the decelerated region whose gradually increasing circulation is directly balanced by the loss of circulation of the surface-parallel vortex. However, the shear forces caused by small amounts of surface contamination and its associated subsurface boundary layer inhibit the connection process by preventing the essential viscous flux of parallel vorticity through the surface. Instead, the subsurface boundary layer is associated with a flux of parallel vorticity into the surface which then concentrates into the observable secondary separation vortex.

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21

Vatistas, Georgios H. "THE OPTICS OF THE COMPRESSIBLE N = 2 VORTEX." Transactions of the Canadian Society for Mechanical Engineering 30, no. 1 (March 2006): 143–66. http://dx.doi.org/10.1139/tcsme-2006-0009.

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This paper deals with the refracted shadows generated by the n = 2 compressible vortex. A more pragmatic picture of the optical phenomenon emerges when the flow instead of being isentropic is permitted to transfer heat and dissipate mechanical energy. The visual side of the formulation adheres to the long-established shadowgraph technique. It is shown that although the constant entropy hypothesis retains the qualitative nature of the phenomenon, the present approach improves on the quantitative side of the problem. It reveals that the central dark disk boundary does not mark the vortex core radius, renders the center of the vortex slightly darker, and the halo considerably brighter than the earlier isentropic flow estimates. Furthermore, it offers an alternative explanation for the peculiar set of alternating dark and bright circular bands that appeared in the shadow imprints of an earlier blade tip vortex experiment. The improved methodology can now be used to advance the experimental description of compressible vortices through shadowgraphy.

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22

Zhang, Yu, Duan Yong Li, and Tao Wu. "Shadowgraph of Pulse CO₂ Laser Induced Breakdown in Different Pressure Air." Advanced Materials Research 887-888 (February 2014): 1001–4. http://dx.doi.org/10.4028/www.scientific.net/amr.887-888.1001.

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The expansion property of an infrared CO2 laser produced air plasma is characterized using a high-speed imaging shadowgraph technique. The shadowgraphs were taken by a time-gated intensified charge-coupled device at various delay times after single pulses induced gas breakdown. We examined five incident laser energy of 180, 240, 345, 420 and 600 mJ induced air breakdown at the pressure of atmospheric and 104 Pa. A shock wave produced by laser induced breakdown was also observed and its speed was measured as a function delay time between the breakdown and the shadow imaging under different air pressure. The experimental results indicated that the radial and axial shock wave front evolutions showed similar behavior, which increased fast with delay time at early stage and slowly at later stage. The propagation speed of the wavefront was about 2 cm/μs at the initial stage of breakdown, and then decreased very quickly. The propagation speed under low air pressure was higher than that of gases under high pressure and the spark sustained less time at lower pressure. The size of laser induced air spark increased with incident laser energy but not simple linear relationships.

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23

Mohammadi, Moein, Jakub L. Nowak, and Szymon P. Malinowski. "Microphysical measurements of hydrometeors using shadowgraph imaging technique." Journal of Physics: Conference Series 2367, no. 1 (November 1, 2022): 012020. http://dx.doi.org/10.1088/1742-6596/2367/1/012020.

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Abstract The size distributions of raindrops and precipitation particles were measured in a series of in situ experiments during various weather events in Warsaw, Poland. To perform the measurements, a shadowgraph instrument, “VisiSize D30”, was set up on the roof of the Institute of Geophysics, University of Warsaw, together with an “OTT Parsivel2” laser disdrometer. The VisiSize D30, recently introduced to atmospheric research, is capable of accurately determining a wide range of particle sizes, from micrometre-scale cloud droplets to millimetre-scale precipitation particles, while directly measuring droplets by capturing shadow images of them. A comparison of the data collected by the two instruments during simultaneous measurements shows that combining the shadowgraph technique with the optical disdrometer can prevent droplet size distribution truncation and provide more accurate results.

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24

Schopf, Wolfgang. "A NEW WAY OF ANALYZING THE SHADOWGRAPH METHOD." Journal of Flow Visualization and Image Processing 4, no. 2 (1997): 179–87. http://dx.doi.org/10.1615/jflowvisimageproc.v4.i2.80.

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Wigley, P. B., P. J. Everitt, K. S. Hardman, M. R. Hush, C. H. Wei, M. A. Sooriyabandara, P. Manju, J. D. Close, N. P. Robins, and C. C. N. Kuhn. "Non-destructive shadowgraph imaging of ultra-cold atoms." Optics Letters 41, no. 20 (October 12, 2016): 4795. http://dx.doi.org/10.1364/ol.41.004795.

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26

Cunningham, J. L., I. Bisbinas, R. Greenwood, and I. D. Learmonth. "Precision of wear measurement using the shadowgraph technique." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 221, no. 8 (August 1, 2007): 899–902. http://dx.doi.org/10.1243/09544119jeim253.

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The shadowgraph technique is a relatively easy-to-use and inexpensive method of wear measurement from explanted acetabular cups. In this technique, from a mould of the internal surface of the cup, measurements of linear wear and wear angle can be obtained, from which volumetric wear can be calculated. In this study the measurement precision of this technique was assessed and the influence of different observers and multiple moulds was also determined. It was found that linear wear (coefficient of variation (CV) = 1.49 per cent) can be more precisely determined than wear angle (CV = 8.18 per cent) and that both the observer and the mould can significantly influence the results obtained, although the influence of the mould is considerably less than that of the observer.

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27

Hargather, Michael J., and Gary S. Settles. "Retroreflective shadowgraph technique for large-scale flow visualization." Applied Optics 48, no. 22 (July 27, 2009): 4449. http://dx.doi.org/10.1364/ao.48.004449.

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28

Jenkins, D. R. "Interpretation of shadowgraph patterns in Rayleigh-Bénard convection." Journal of Fluid Mechanics 190 (May 1988): 451–69. http://dx.doi.org/10.1017/s0022112088001405.

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The relationship between observations of cellular Rayleigh-Bénard convection using shadowgraphs and theoretical expressions for convection planforms is considered. We determine the shadowgraphs that ought to be observed if the convection is as given by theoretical expressions for roll, square or hexagonal planforms and compare them with actual experiments. Expressions for the planforms derived from linear theory, valid for low supercritical Rayleigh number, produce unambiguous shadowgraphs consisting of cells bounded by bright lines, which correspond to surfaces through which no fluid flows and on which the vertical component of velocity is directed downwards. Dark spots at the centre of cells, indicating regions of hot, rising fluid, are not accounted for by linear theory, but can be produced by adding higher-order terms, predominantly due to the temperature dependence of a material property of the fluid, such as its viscosity.

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29

Little, Adrienne B., and Srinivas Garimella. "Shadowgraph visualization of condensing R134a flow through ejectors." International Journal of Refrigeration 68 (August 2016): 118–29. http://dx.doi.org/10.1016/j.ijrefrig.2016.04.018.

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Adam, Abdullah, Mamat Rizalman, and Tomoaki Yatsufusa. "Analysis of Diesel Spray Droplets Behavior Using Shadowgraph Technique Images." International Journal of Materials, Mechanics and Manufacturing 3, no. 1 (2015): 60–64. http://dx.doi.org/10.7763/ijmmm.2015.v3.167.

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31

Espenhahn, Björn, Lukas Schumski, Christoph Vanselow, Dirk Stöbener, Daniel Meyer, and Andreas Fischer. "Feasibility of Optical Flow Field Measurements of the Coolant in a Grinding Machine." Applied Sciences 11, no. 24 (December 7, 2021): 11615. http://dx.doi.org/10.3390/app112411615.

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For industrial grinding processes, the workpiece cooling by metalworking fluids, which strongly influences the workpiece surface layer quality, is not yet fully understood. This leads to high efforts for the empirical determination of suitable cooling parameters, increasing the part manufacturing costs. To close the knowledge gap, a measurement method for the metalworking fluid flow field near the grinding wheel is desired. However, the varying curved surfaces of the liquid phase result in unpredictable light deflections and reflections, which impede optical flow measurements. In order to investigate the yet unknown optical measurement capabilities achievable under these conditions, shadowgraphy in combination with a pattern correlation technique and particle image velocimetry (PIV) are applied in a grinding machine. The results show that particle image velocimetry enables flow field measurements inside the laminar metalworking fluid jet, whereby the shadowgraph imaging velocimetry complements these measurements since it is in particular suitable for regions with spray-like flow regimes. As a conclusion, optical flow field measurements of the metalworking fluid flow in a running grinding machine are shown to be feasible.

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32

Martínez-González, Adrián, David Moreno-Hernández, Miguel León-Rodríguez, César Carrillo-Delgado, and Enrique Cossío-Vargas. "Simultaneous Schlieren-Shadowgraph Visualization and Temperature Measurement Fields of Fluid Flow Using One Color CCD Camera." Sensors 22, no. 23 (December 6, 2022): 9529. http://dx.doi.org/10.3390/s22239529.

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Visualizing two variables in the fluid flow requires a complex optical system to fulfill such a purpose. Furthermore, in these applications, measuring the temperature fields of the fluid is sometimes necessary. In this work, we use a color digital camera to record in one snapshot shadowgraph and two direction sensitivity Schlieren images. Furthermore, the Schlieren images obtained are used to measure temperature fields. The optical system, as main components, employs an rgb Light Emitting Diode (LED), two knife edges represented by shortpass and longpass ultra-thin filters, and a color digital camera. The results of this study show that shadowgraph images are contaminated with the crosstalk effect, and correction against it was applied. On the other hand, the reached resolution of the optical system to measure temperature values is approximately one degree.

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Szabo, Peter S. B., Antoine Meyer, Martin Meier, Vasyl Motuz, Yaraslau Sliavin, and Christoph Egbers. "Simultaneous PIV and shadowgraph measurements of thermo-electrohydrodynamic convection in a differentially heated annulus." tm - Technisches Messen 89, no. 3 (January 21, 2022): 148–57. http://dx.doi.org/10.1515/teme-2021-0120.

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Abstract Convection in a silicone oil with a temperature dependant fluid property is investigated experimentally in a differentially heated cylindrical annulus. A convective flow is induced by terrestrial gravity in axial direction and combined with an electrical tension applied between both cylinders to induce thermo-electrohydrodynamic convection. To capture the evolving velocity and temperature fields a novel combination of simultaneous PIV and shadowgraph technique is utilized. Results reveal azimuthal modes with cold and hot jets from inner and outer cylinder that are referred to the electric tension. The lack of information in the shadowgraph pictures were recovered by the PIV technique providing a deeper understanding in the nature of the development of the azimuthal mode number and the surrounding axial flow of natural convection. In addition, the results provide a robust framework in the capability of combining both techniques to investigate complex flow patterns that are non-axisymmetric.

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Disimile, Peter J., Norman Toy, and L. Swanson. "A LARGE-SCALE SHADOWGRAPH TECHNIQUE APPLIED TO HYDRODYNAMIC RAM." Journal of Flow Visualization and Image Processing 16, no. 4 (2009): 303–32. http://dx.doi.org/10.1615/jflowvisimageproc.v16.i4.30.

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35

Cifuentes, A., S. Alvarado, H. Cabrera, A. Calderón, and E. Marín. "Thermal diffusivity measurement by lock-in photothermal shadowgraph method." Journal of Applied Physics 119, no. 16 (April 28, 2016): 164902. http://dx.doi.org/10.1063/1.4947454.

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36

Settles,, GS, and EE Covert,. "Schlieren and Shadowgraph Techniques: Visualizing Phenomena in Transport Media." Applied Mechanics Reviews 55, no. 4 (July 1, 2002): B76—B77. http://dx.doi.org/10.1115/1.1483362.

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37

Hirschberg, A. "Schlieren and Shadowgraph Techniques: Visualizing Phenomena in Transparent Media." European Journal of Mechanics - B/Fluids 21, no. 4 (January 2002): 493. http://dx.doi.org/10.1016/s0997-7546(02)01191-3.

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38

Li, Jiaqi, Siyao Shao, and Jiarong Hong. "Machine learning shadowgraph for particle size and shape characterization." Measurement Science and Technology 32, no. 1 (October 31, 2020): 015406. http://dx.doi.org/10.1088/1361-6501/abae90.

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39

Matthujak, Anirut, Chaidet Kasamnimitporn, Wuttichai Sittiwong, and Kulachate Pianthong. "Visualization of Supersonic Non-Newtonian Liquid Jets." Applied Mechanics and Materials 187 (June 2012): 63–67. http://dx.doi.org/10.4028/www.scientific.net/amm.187.63.

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This paper describes the characteristics of supersonic non-Newtonian liquid jets injected in ambient air. The main focus is to visualize three types of time-independent non-Newtonian liquid jet and to describe their behaviors. Moreover, comparisons between their dynamic behaviors with Newtonian liquid jet are reported. The supersonic liquid jets are generated by impact driven method in a horizontal single-stage power gun. Jets have been visualized by the high speed digital video camera and shadowgraph method. Effects of different liquid types on the jet penetration distance, average jet velocity and other characteristics have been examined. From shadowgraph images, the unique dynamic behaviors of each non-Newtonian liquid jets are observed and found obviously different from that of the Newtonian liquid jet. The maximum average jet velocity of 1,802.18 m/s (Mach no. 5.30) has been obtained. The jet penetration distance and average velocity are significantly varied when the liquid types are different.

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Weigand, A., and M. Gharib. "Turbulent Vortex Ring/Free Surface Interaction." Journal of Fluids Engineering 117, no. 3 (September 1, 1995): 374–81. http://dx.doi.org/10.1115/1.2817272.

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The interaction of turbulent vortex rings that approach a clean water surface under various angles is experimentally investigated. The temporal evolution of the vortex rings with an initial Reynolds number of Re0 = 7500 is characterized by the laminar/turbulent transition and asymptotic relaminarization of the flow. Using the shadowgraph technique, two major flow cases were identified as a result of the vortex-ring/free-surface interaction: a trifurcation case that results from the interaction during the transition stage, and a bifurcation case that evolves during the fully-developed turbulent stage. In contrast to the laminar interaction, the turbulent bifurcation pattern is characterized by the reconnection and mutual interaction of many small-scale structures. Simultaneous digital particle image velocimetry (DPIV) and shadowgraph measurements reveal that the evolution of the small-scale structures at the free surface is strongly dominated by the bifurcation pattern, which in turn is a consequence of the persisting laminar sublayer in the core regions of the reconnected turbulent vortex loops.

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41

Fujisawa, Nobuyuki, Takayuki Yamagata, Ryotaro Seki, and Motofumi Ohki. "Erosion Mechanism of a Cavitating Jet on Groove Roughness." Fluids 6, no. 1 (December 26, 2020): 6. http://dx.doi.org/10.3390/fluids6010006.

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The erosion behavior of a cavitating jet on groove roughness was investigated experimentally using mass-loss characteristics, scanning electron microscopy (SEM) observation, time-resolved shadowgraph, and schlieren flow visualizations. The wall morphology of the cavitating-jet erosion on the groove roughness indicated an increased mass loss, which was highly increased along the groove rather than across the groove. Furthermore, increased erosion pits were observed on the groove bottom along the grooves. The shadowgraph imaging of the cavitating jet on the rough wall showed noncircular cavitation bubble distributions along and across the grooves, which corresponds to the increased number of cavitation bubbles along the grooves and the decreased number of bubbles across the grooves. This result is consistent with the erosion morphology of the groove roughness. Schlieren imaging indicated that the frequency and intensity fluctuation of the shockwave formation did not change significantly on the groove roughness along and across the grooves. The findings in the study show that the increased erosion mechanism on groove roughness is caused by the increased number of impulsive forces and the shockwave focusing effect on the groove bottom.

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Rajkumar, S., S. M. Aravindh Kumar, and P. Vasanthakumar. "EFFECT OF COFLOW ON SONIC JET." Journal of Physics: Conference Series 2054, no. 1 (October 1, 2021): 012079. http://dx.doi.org/10.1088/1742-6596/2054/1/012079.

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Abstract The sonic coflow effect on the core length of sonic primary jet was experimentally investigated in this research work. A circular convergent nozzle was used for both core and coflow jet studies. The 1mm annular gap was maintained between the coflow and core nozzles. The nozzle pressure ratio (NPR) was varied from 3 to 5, insteps of 1 for both the nozzles. For each primary NPR, the NPR of coflow was varied, and the shadowgraph flow visualization was carried out. From the shadowgraph visualization results it was observed that the sonic primary jet core length increases with increasing pressure ratio without coflow. With sonic coflow, the primary jet core length started to increase further with increasing coflow NPR. That is, the increase of sonic coflow NPR at each sonic primary jet NPR resulted in the elongation of core. Therefore, the introduction of coflow has resulted in core length elongation at all the levels of underexpansion. The primary jet core elongation due to the presence of coflow resulted in the weakening of shock strength in the primary jet core.

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43

Méthivier, Lucas, Romane Braun, Francesca Chillà, and Julien Salort. "Turbulent transition in Rayleigh-Bénard convection with fluorocarbon^(a)." Europhysics Letters 136, no. 1 (October 1, 2021): 10003. http://dx.doi.org/10.1209/0295-5075/ac34d4.

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Abstract We present measurements of the global heat transfer and the velocity field in two Rayleigh-Bénard cells (aspect ratios 1 and 2). We use Fluorinert FC770 as the working fluid, up to a Rayleigh number . The velocity field is inferred from sequences of shadowgraph pattern using a Correlation Image Velocimetry (CIV) algorithm. Indeed the large number of plumes, and their small characteristic scale, make it possible to use the shadowgraph pattern produced by the thermal plumes in the same manner as particles in Particle Image Velocimetry (PIV). The method is validated in water against PIV, and yields identical wind velocity estimates. The joint heat transfer and velocity measurements allow to compute the scaling of the kinetic dissipation rate which features a transition from a laminar scaling to a turbulent Re 3 scaling. We propose that the turbulent transition in Rayleigh-Bénard convection is controlled by a threshold Péclet number rather than a threshold Rayleigh number, which may explain the apparent discrepancy in the literature regarding the “ultimate” regime of convection.

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Hall, R. M., A. Unsworth, P. S. Craig, C. Hardaker, P. Siney, and B. M. Wroblewski. "Measurement of Wear in Retrieved Acetabular Sockets." Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 209, no. 4 (December 1995): 233–42. http://dx.doi.org/10.1243/pime_proc_1995_209_350_02.

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Twenty-eight standard Charnley sockets were retrieved at revision surgery. The penetration angle with respect to the cup coordinate system, β, and penetration depth, d, of the sockets were measured using both the traditional shadowgraph technique and by analysing data obtained from a coordinate measuring machine (CMM). In addition, d was deduced radiographically from pre-revision X-rays. Limits of agreement between the three methods of measuring d were of the order of ±0.5 mm. Using the data obtained from the CMM it was possible to deduce the wear volume Vmeas directly. It was found that, in general, values of the wear volume calculated from d and β using equations cited elsewhere (1, 2) were both imprecise and inaccurate. The direct measurement of the wear volume using the CMM depends on the location of reference points external to the wear surface. If such surfaces were damaged, then it was concluded that the shadowgraph technique provided the most suitable method for measuring the dimensional changes in the retrieved socket, due to its relative ease of use.

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Sabbagh, Reza, Mohammad Amin Kazemi, Hirad Soltani, and David S. Nobes. "Micro- and Macro-Scale Measurement of Flow Velocity in Porous Media: A Shadow Imaging Approach for 2D and 3D." Optics 1, no. 1 (February 25, 2020): 71–87. http://dx.doi.org/10.3390/opt1010006.

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Flow measurement in porous media is a challenging subject, especially when it comes to performing a three-dimensional (3D) velocimetry at the micro scale. Volumetric flow measurement techniques such as defocusing and tomographic imaging generally involve rigorous procedures, complex experimental setups, and multi-part data processing procedures. However, detailed knowledge of the flow pattern at the pore and subpore scales is important in interpreting the phenomena that occur inside the porous media and understanding the macro-scale behaviors. In this work, the flow of an oil inside a porous medium is measured at the pore and subpore scales using refractive index matching (RIM) and shadowgraph imaging techniques. At the macro scale, flow is measured using the particle image velocimetry (PIV) method in two dimensions (2D) to confirm the volumetric nature of the flow and obtain the overall flow pattern in the vicinity of the flow entrance and at the far field. At the micro scale, the three-dimensional (3D) flow within an arbitrary volume of the porous medium was quantified using 2D particle-tracking velocimetry (PTV) utilizing the law of conservation of mass. Using the shadowgraphy method and a single camera makes the flow measurement much less complex than the approaches using laser light sheets or multiple cameras with multiple viewing angles.

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Farahani, M., and A. Jaberi. "Study of buzz phenomenon using visualization of external shock structure." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 7 (June 27, 2018): 2690–98. http://dx.doi.org/10.1177/0954410018785261.

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An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and shock displacement were measured by inspection of visualization pictures in each test. The obtained data from shadowgraphs were compared with those obtained from pressure measurements, and good agreement was found between them. The results revealed that for a moderate value of mass flow rate, the frequency of shock oscillation decreases as Mach number increases. Further, by increasing angle of attack, the shock displacement of oscillation will increase. At non-zero angles of attack, the displacement and frequency of shock motion show different behaviors on the leeward and windward sides of the body.

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Glosse, Philipp, Stefan Denneler, Oliver Stier, and Ralf Moos. "Investigation of the Powder Aerosol Deposition Method Using Shadowgraph Imaging." Materials 14, no. 10 (May 12, 2021): 2502. http://dx.doi.org/10.3390/ma14102502.

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The powder aerosol deposition method (PAD) is a vacuum-based spray coating technology. It allows for production of highly dense coatings at room temperature, especially of brittle-breaking materials. This yields new options for coating substrate materials that even melt at low temperatures. The film formation mechanism is called room temperature impact consolidation (RTIC). The occurrence of this mechanism is strongly linked to the gas jet used in the process. The velocity and direction of the particles in the gas jet forming between the nozzle orifice and the substrate are the main factors influencing the quality of the coating. This dependency aimed to be elaborated with a measurement setup and coating experiments and is shown in this work. We investigated the gas jet formation using a shadow optical imaging system. Regions of different gas density are visualized by this technique. Several parameter sets, in particular gas flow rates and chamber pressures, were investigated. In addition, coatings were produced on glass substrates with the same parameters. As a coating material, the superconducting ceramic-like magnesium diboride (MgB2) was chosen. A correlation between shadow images and thickness profiles of the coatings shows how the gas jet formation affects the uniformity of thickness. Shadow optical images provide valuable information on the flight direction of the particles and allow validation of simulation results.

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Omura, Ryosuke, Yuta Shimazaki, Shin Yoshizawa, and Shin-ichiro Umemura. "Quantitative Measurement of Focused Ultrasound Pressure Field Using Subtraction Shadowgraph." Japanese Journal of Applied Physics 50, no. 7S (July 1, 2011): 07HC07. http://dx.doi.org/10.7567/jjap.50.07hc07.

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OGAWA, Yohei, Takeo TOMITA, Yoshio NUNOME, Hideo SUNAKAWA, Takashi KOGANEZAWA, and Tatsuya KOMARU. "S054064 Visualization of LOX jet using high-speed shadowgraph imaging." Proceedings of Mechanical Engineering Congress, Japan 2013 (2013): _S054064–1—_S054064–4. http://dx.doi.org/10.1299/jsmemecj.2013._s054064-1.

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50

Wang, Shihua. "Optical micro-shadowgraph-based method for measuring micro-solderball height." Optical Engineering 44, no. 5 (May 1, 2005): 050506. http://dx.doi.org/10.1117/1.1906003.

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