This laboratory study focused on the effect of a submerged vane-field on the flow pattern and bed morphology near and inside the entrance reach of a movable bed 90° lateral diversion. The system was modelled under live bed conditions for a water discharge ratio of ≈0.2. Two experiments were run until bed equilibrium was reached: with and without a vane-field installed close to the diversion entrance to control the transfer of sediments into the diversion channel. The equilibrium bed morphology and the associated 3D flow field were measured in great detail. The bed load diverted into the diversion was reduced by approximately one quarter due to the action of the vane-field. The vanes prevented the formation of the diversion vortex in the main channel, upstream of the diversion’s entrance, thus contributing to that decrease. They also created a main channel vortex that started at the most upstream vanes and further decreased the amount of bed load entering the diversion. The flow separation zone inside the diversion was larger with vanes, but conveyance was balanced through a slightly deeper scour trench therein. The flow structures described were confirmed through the measurements of the turbulent kinetic energy.
A lateral diversion channel diverts part of the flow from another channel, frequently termed main channel and alters the flow structure and hydraulic conditions in the vicinity of its entrance, impacting on the bed morphology [1] and sediment fluxes. In this study, the turbulence structure in the vicinity of a lateral water intake was investigated by performing the quadrant analysis (see Fig. 1) of a number velocity records collected at different locations of a lateral water intake built at the Hydraulics Laboratory of Instituto Superior Técnico. The length and width of the rectangular main channel were 9.28 m and 0.68 m, respectively, whereas those of the diversion channel were 2.0 m and 0.26 m. The diversion angle was θ = 90°. Both channel beds were composed of a layer of sand characterized by a median diameter, D50, equal to 0.86 mm and a gradation coefficient, σD, equal to 1.35. Two experiments were conducted under live bed flow conditions until the bed morphology reached the equilibrium stage. 3D velocity measurements were made through an ADV device, working at a sampling frequency of 100 Hz. Quadrant analysis showed a coherent agreement with the average mean velocity field presented in a previous paper published by the authors [2].
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