THREE-DIMENSIONAL PTV MEASUREMENT OF MIXING FLOW BY BUBBLING JET IN A CYLINDRICAL VESSEL

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This project aims to measure three-dimensional motion and paths of fluid elements in a cylindrical water bath into which a bubbling jet is blown from the center of the bottom. Main effort is paid to develop a new efficient three-dimensional PTV method which can work on a personal computer system with a practical performance. In order to measure three-dimensional velocity vectors efficiently using a personal computer system, following three algorithms are newly developed:1) Measuring method of three-dimensional co-ordinates of tracer particles.2) A method for compensating the influence of refraction at the air-water boundary.3) Algorithm of three-dimensional binary-image correlation method.A two-camera-stereo system is planned for measuring three-dimensional co-ordinates of tracer particles at first, but it is found that the system is not reliable enough to determine stereo-pairs from a pair of pictures which contain more than 50 tracers. Then three-camera system is developed to satisfy the requested performance. Results of some preliminary experiments show satisfactorily performances of the measuring system.