Assessment of Sediment Capture Performances of Coanda and Tyrolean Intakes by Experiments

Intake structures on channels or in reservoirs are frequently used to divert/withdraw a certain amount of water discharge for various purposes of use such as irrigation, potable water supply and generation of hydroelectric power. Hydrologic, geotechnical, topographic and climatic factors directly affect the type of the intake structures which will be constructed. Factors such as excessive rain or snow melt and greater river bed slope which can be cause of high flow rate make impossible to use of the frontal and lateral intake structures. When water has to be diverted from a turbid source having great amount of suspended materials in it, bottom intakes structure such as Coanda and Tyrolean types are preferred. To perform this task, diverted water is captured by a transversal rack and a gallery located in the control crest is utilized. With a proper design of the intake, the quality of the diverted water can be increased by screening out most of the sediments in the flow. Previous studies on the bottom intake structures, presented empirical equations based on experiments relating the diverted water amount per unit width to hydraulic head, discharge coefficient and void ratio of the bar clearance to the total length. Most studies focused on the discharge coefficient and the parameters affecting this coefficient such as hydraulic and rack characteristics. Presented study focused on the sediment capture performances of these two specific type intake structures though experimental work. A novel sediment feeding system designed specifically for this study is utilized in the experiments. Study results pointed out a new parameter including sediment characteristics, as well as rack and hydraulic characteristics should be considered for a proper design of Tyrolean and Coanda type intakes.