This paper describes three-dimensional particle tracking velocimetry (3D PTV), which enables us to obtain remarkably larger number of velocity vectors than previous techniques. Instead of the usual stereoscopic image recordings, the present 3D PTV visualizes an entire three-dimensional flow with the scanning laser-light sheets generated from a pair of optical scanners and the images are taken by a high-speed video system synchronized with the scannings. The digital image analyses to derive velocity components are based on the numerical procedure (Ushijima and Tanaka, 1994), in which several improvements have been made on the extraction of particle images, the determination of their positions, the derivation of velocity components and others. The present 3D PTV was applied to the rotating fluids, accompanied by Ekman boundary layers, and their complicated secondary flow patterns, as well as the primary circulations, are quantitatively captured.
Determination of the coefficients of Langevin models for inhomogeneous turbulent flows by three-dimensional particle tracking velocimetry and direct numerical simulation