Three-Dimensional Structure of the Flow at an Open-Channel Confluence

Abstract

Flow at an open-channel confluence is characterized by a free shear layer formed between converging flows and a separated shear layer formed from the downstream side of the junction. These shear layers are closely related to the formation of secondary flows at the confluence, which is of great importance in river engineering. In this study, three-dimensional turbulence characteristics of the flow at a right-angled open channel confluence accompanying these flow structures are investigated by turbulence measurements and a visualization of the near-wall flow by an oil-film method. From the experimental results, existences of a descending secondary flow along the free shear layer and a strong helicoidal flow accompanying a weak counter-rotating secondary flow along the separated shear layer are verified.