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Particle Tracking Velocimetry (PTV) is a velocimetry method i.e. a technique to measure velocity of particles that are resident in a fluid. As the name suggests, individual particles are tracked, so this technique is a Lagrangian approach. In contrast to Particle Image Velocimetry (PIV), which is an Eulerian method that measures the velocity field of a fluid at a (rectangular) grid. There are two very different experimental methods: * the two-dimensional (2D) PTV, in which the flow field is measured in the two-dimensional slice of the flow, illuminated by a laser sheet (a thin plane) and low density of seeded particles allow for the tracking each of them individually for several frames. * the Three-Dimensional Particle tracking velocimetry (3D-PTV) is a distinctive experimental technique, based on multiple camera-system, three-dimensional volume illumination and tracking of flow tracers (i.e. particles) in three-dimensional space by using photogrammetric principles. ==Description== A typical installation of the 3D-Particle tracking velocimetry consists of three or four digital cameras, installed in an angular configuration, synchronously recording the diffracted or fluorescent light from the flow tracers, seeded in the flow. The flow is illuminated by a collimated laser beam, or by another source of light. There is no restriction on the light to be coherent or monochromatic and only its illuminance has to be sufficient to illuminate the observational volume. Particles or tracers could be fluorescent, diffractive, tracked through as many as possible consecutive frames on as many cameras as possible. In principle, two cameras in the stereoscopic configuration are sufficient in order to determine the three coordinates of a particle in space, but in most practical situations, three or four cameras are necessary. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Particle tracking velocimetry」の詳細全文を読む スポンサード リンク
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