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Visualised image analysis

In this method, a visualised image is put into a still or video camera so that its density values are digitised. It is then put into a computer to be processed analytically, statistically, in colour distribution and otherwise, and thus is made much easier to interpret. Various techniques for this method have been developed. Among them, PIV (Particle Imaging Velocimetry) in particular has recently been popular. As an example of PTV (Particle Tracking Velocimetry), Plate 11 shows the velocity vectors obtained for flow over a cylinder by following, from time to time, the spherical plastic tracer particles of diameter 0.5mm suspended in the water.” Plate 12 is an example of an image treated by a density correlation method. The image was obtained by injecting a smoke tracer into the room from the floor under the chair on which a man was sitting and natural convection around a human body was visualised an example of the hydrogen bubble technique M. A., Atlas of Visualization, Vol. 1 (1992), 197. Karman vortex street behind a cylinder (hydrogen tube method): (a) visualised image; (b) binarisation; (c) change to fine line; (d) velocity vector; (e) velocity vector at grid point where the time line and the streak line are visualised simultaneously. The visualised image is caught by a CCD camera, converted to binary codes and fine lines, and thus the velocity vector is obtained.” In Plate 4, the flow around a cone flying at supersonic speed is visualised by the laser holographic interferometer method, and the density distribution on a section is obtained by the computer tomography method.