Analysis of Surface-flow Patterns at a Right-Angled Open-Channel Confluemce by an Image Processing Technique

Abstract

Two-dimensional water-surface flow structure at a right-angled open-channel confluence is investigated by applying an image processing technique. In this study, the correlation method is used to obtain instantaneous velocity distributions. From the successive twodimensional velocity distributions, unsteady features of a saparation bubble at the confluence for different discharge ratios and the Reynolds numbers are investigated.The result shows that the separation bubble is distorted into two or three groups of vortices at low frequency and a distorted vortex-group moves downstream at a speed of about halfof the main-stream velocity. Turbulent characteristics obtained by the correlation method agree well with the results by point measurements near the water-surface.