Although combining flows are common in natural streams, no comprehensive experimental data has been compiled to characterize the three-dimensional flow field within the compound channel confluence. The present study examines the time-averaged flow structure at confluence over a rigid bed. Current knowledge of channel confluence, based on laboratory observation indicates that cross flow interactions exert a significant influence on confluence events. Secondary current and turbulent stresses are reproduced well by the hydraulic model and found greater in the interface region as relative flow ratio decreases. Velocity fields in combining flow region arising from varying discharge ratios are presented. A zone of depression in surface elevation in compound channel junction is observed as well. The flow field in compound channel is seen to be moderately different from that of simple channel junction. This study contributes to a better knowledge of hydraulic key processes into fundamental aspect of combining flow dynamics.
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