Role of bed elevation discordance at 90 degrees straight-channel confluences

Abstract

This paper aims at studying the role of difference in bed elevations between the tributary and main canals (Delta z(T)) in 90 degrees confluence under different hydrologic/hydraulic conditions. To do this, 3D finite-volume model is used. Four Delta z(T)/ h(d) values in the range [0.0, 0.5] (where h(d) stands for the flow depth in the main canal at the confluence) and three values of the discharge ratio D-R = Q(MR)/Q(tot) ={0.250, 0.583, 0.750} are considered. It is found that the: 1) increase in Delta z(T) attenuates 3D flow at the confluence and enhances 3D flow in the post-confluence canal, 2) enhanced 3D flow affects the existence, size and position of the recirculation zone (RZ), 3) size of the RZ reduces as Delta z(T) increases, 4) maximal shear is attained in the upper layers when Delta z(T) gt 0 and 5) zone of tau(0,max) reduces and moves to the downstream junction corner as Delta z(T) increases.