Experiments on flow at a 90 degrees open-channel junction

Although open-channel junctions are common in many hydraulic structures, no comprehensive data set has been compiled that describes the 3D flow field within the junction itself. This physical model study examined a 90 degrees , sharp-edged, open-channel junction for channels of equal width. Depth mea surements were made using a point gauge while velocity measurements were ta ken using an acoustic doppler velocimeter over a grid defined throughout th e junction region. The average velocity and turbulence intensity were calcu lated from a time series of velocities that was recorded at each location. In addition, a 2D mapping of the water surface was performed on a 76.2 mm s quare grid throughout the channel junction. This paper presents the details of the experimental procedure and the general flow characteristics observe d. The full data set generated during this experimental work is available f or downloading on the Internet. Using a small portion of the data recorded, an evaluation of several previously proposed theories of combining flow in open-channel junctions is presented. This has revealed that the simplified mathematical model gives reasonable prediction of the experimental results . The complete data set describing combining flows at a 90 degrees open-cha nnel junction is presented as a resource for the validation of 3D computati onal fluid dynamics codes that utilize a free-surface model.