PARTICLE IMAGE VELOCIMETRY BY STEREOSCOPIC COMPUTATIONAL VISION - S-PIV-3D SYSTEM

Abstract

The PIV system developed, by computational vision techniques, entitled S-PIV-3D, includes features as the optical method of image acquisition and the calibration process. The measurement system, resulted from these characteristics, uses a single conventional digital video camera to obtain three-dimensional data in low turbulence flow, a fact that provided significant economy in the system implantation. The acquisition of images is accomplished through an optical device built on a stereoscope that promotes the acquisition from two different viewpoints. The calibration process, that uses a calibration target and a transformation function, allows the calculation of the real coordinates and the free positioning of images production and acquisition devices. Results present fields of three-dimensional velocities obtained through specific software. The software, besides calibration functions, image processing and results, contains parts developed for specific applications as, for instance, the obtaining of vertical velocities in the surface of free flows and others. To test the measurement system a water tunnel prototype was developed to measure and visualize several situations involving especially the didactic demonstration of cinematic behaviour of the flow around solid models. The measurement system permits flow diagnosis and flow visualization through interactive graphics for the vectorial velocity fields and slow motion videos. An engineering application was developed at the oscillating grids thank. In this thank the obtained data are related to the reaeration coefficient K₂ for estimation of water body's natural depuration.