shadowgraph

shad·ow·graph

S0309500 (shăd′ō-grăf′)n.1. An image produced by casting a shadow on a screen.2. See shadow play.3. See radiograph.

shadowgraph

(ˈʃædəʊˌɡrɑːf; -ˌɡræf) n1. a silhouette made by casting a shadow, usually of the hands, on a lighted surface2. (Photography) another name for radiograph

shadowgraph

an image formed by a shadow cast upon a lighted surface, as one formed by the hands for entertainment. — shadowgraphist, n.See also: Performing

Thesaurus

Noun

shadowgraph - a photographic image produced on a radiosensitive surface by radiation other than visible light (especially by X-rays or gamma rays)radiograph, skiagram, skiagraph, radiogramautoradiograph - a radiogram produced by radiation emitted by the specimen being photographedphoto, photograph, pic, exposure, picture - a representation of a person or scene in the form of a print or transparent slide; recorded by a camera on light-sensitive materialroentgenogram, X-ray photograph, X-ray picture, X ray, X-ray - a radiogram made by exposing photographic film to X rays; used in medical diagnosis

shadowgraph

Shadowgraph

An optical method of rendering fluid flow patterns visible by using index-of-refraction differences in the flow. The method relies on the fact that rays of light bend toward regions of higher refractive index while passing through a transparent material. The fluid is usually illuminated by a parallel beam of light. The illustration depicts the method as it might be applied to a fluid sample undergoing thermal convection between two parallel plates, with the lower plate being kept warmer than the upper one. As illustrated, the rays bend toward the cooler down-flowing regions, where the refractive index is higher, and away from the warmer up-flowing ones. After they have passed through the fluid layer, the rays tend to focus above the cooler regions and defocus above the warmer regions. If an image of the light beam is recorded not too far from the sample, brighter areas of the image will lie above regions of down flow, where the rays have been concentrated, and darker areas will lie above regions of up flow. Because the light passes completely through the sample, the bending effect for each ray is averaged over the sample thickness. See Convection (heat), Refraction of waves

Schematic of the shadowgraph method applied to reveal convection patterns in a fluid layer

In convection experiments the refractive index varies because of thermal expansion of the fluid, but the method is not restricted regarding the mechanism responsible for disturbing the refractive index. Thus the same method may be used to visualize denser and less dense regions in a gas flowing in a wind tunnel, including Mach waves and shock waves, where the denser regions have a higher-than-average refractive index. See Shock wave, Supersonic flow

Images are usually recorded by means of a charge-coupled-device (CCD) camera, digitized, and stored in a computer. Such a digitized image consists of an array of numbers, each number being proportional to the brightness at a particular point in the image. The image points (pixels) form a closely spaced rectangular grid. A reference image may be taken in the absence of any fluid flow, and the reference image may be divided point by point into images taken with the fluid moving.

shadowgraph

[′shad·ō‚graf] (graphic arts) A photographic image in the form of a shadow. radiograph (optics) A simple method of making visible the disturbances that occur in fluid flow at high velocity, in which light passing through a flowing fluid is refracted by density gradients in the fluid, resulting in bright and dark areas on a screen placed behind the fluid.

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shad·ow·graph

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Synonyms for shadowgraph

noun a photographic image produced on a radiosensitive surface by radiation other than visible light (especially by X-rays or gamma rays)

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