Investigation of flow at a right-angled lateral intake

Based on experimental measurements and observations in a laboratory channel, the hydrodynamic behaviour of the approaching flow and the amount of sediment entering a right-angled lateral intake in a diversion dam were investigated. The velocity field, both upstream of the intake in the main channel and in front of the intake in the sluiceway, were measured under various discharge combinations of the river, intake and sluice gate. In addition, velocity profiles both upstream and downstream of the intake and the amount of sediment entering it were measured. Analysis of the velocity data showed that the discharge of the sluice gate played an important role in determining the velocity profile and also the mechanism of sediment entry. All velocity profiles where the sluice gate 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. Experimental observation showed that sediment entered the intake by a tornado-like vortex. The strength and frequency of the vortices depended on the intake and sluice gate discharges. Analysis of the sedimentation data showed that the amount of sediment entering the intake increased with increasing intake discharge. In addition, an increase in the sluice gate discharge caused an increase of sediment entry to the intake under the same intake discharge.