flow pattern

Flow passing through lateral intakes and channel junctions is turbulent. Sediment flow and bed forms are affected by these flow patterns and vice versa. In this research, a laboratory study was carried out to explore a possible method for sediment control for a set of submerged vanes and a single spur dike simultaneously. Since a larger portion of the near-bed flow was diverted, the intake received a relatively large amount of bed load material; thus, appropriate and reliable methods were needed to minimize the amount of diverted sediment materials into the intake channel. The submerged vane creates a tip vortex and then the helical flow downstream reduces movement of bed sediment into the diversion. In this study, the optimum dimension, number and array of vanes were selected as determined by the regular design method. To guide flow into the diversion and increase vane performance, a single spur dike was utilized at the opposite side of the intake channel. The location, length and angle of the spur dike were optimized usingthe results of previous testing. The flow patterns for three diversion ratios (13%, 18%, and 24%) and a 25 cm spur dike positioned 80 cm from the intake at a 45° angle. The flow depth was measured using a point gauge and three dimensional velocities (u, v, w) at five levels above the bed as measured by ADV. After the sediment flow reached equilibrium, the channel bed was fixed. The length of separation at the intake channel was decreased by increasing the diversion ratio. By setting a spur dike opposite to the intake channel, the width of the separation line decreased at the channel bottom and increased at the surface, decreasing the amount of sediment ingestion in the intake channel.

The hydrodynamic behavior of approaching flow and the amount of sediment entry into right-angled lateral intakes in diversion dams were investigated using a laboratory channel by experimental measurement and observation. The velocity field upstream of the intake in the main channel and before it at the sluice gate was measured at different elevations of flow at different discharge rates of the river, intake and sluice gate. Velocity profiles were also measured from upstream to downstream for the intake and the amount of sediment entry into it. Analysis of the velocity data showed that discharge at the sluice gate strongly affected velocity profiles and the mechanism of sediment entry. All velocity profiles where the sluice was closed had an inflection point, where the flow direction changed, leading to a return velocity near the bed. The elevation of this point was a function of the intake discharge and approximately equal to the height of the entrance sill. Observation showed that sediment entered the intake in whirlpool vortices. The strength and frequency of the vortices depended on the intake and sluice gate discharges. Analysis of sedimentary data showed that the amount of sediment entering the intake increases with an increase in intake discharge. In addition, for any given intake discharge rate, an increase in the sluice gate discharge caused an increase in sediment entry into the intake.