Abstract
Image analysis method has come to be an efficient tool to measure turbulent flows and several commercial systems are available at present. Most of the systems utilize a particle image velocimetry (PIV) technique based on a pattern matching technique. However, the accuracy of this technique becomes not sufficient under a flow with highly shearing deformation. Thus, in this study, the particle tracking velocimetry (PTV), which has a higher spatial resolution and accuracy than PTV, is used instead for measuring mean and turbulent quantities of open-channel flows. The experiments were performed using a transparent open-channel flume having a width of 0.15m and a high-speed video camera (HAS 200R) with 200fps was used for imaging. As a preliminary experiment, velocity distribution at a longitudinal vertical section of a uniform flow was measured by two PTV techniques and their accuracy and efficiency were verified. Three-dimensional measurement was performed for the flow around a rectangular obstacle placed on one side of the channel wall. Here the three-dimensional information was obtained by combining 2-D PTV results for the laser light sheets (LLS) separately placed in seven horizontal and fourteen vertical planes. It was made clear that two and three dimensional mean and turbulent velocity fields can be obtained with a reasonable accuracy by the presented PTV procedure.
