Determination of optimum rack angle of tyrolean type water-intake structures

Melek, Abiddin Berhan
Tyrolean weir is known as an effective device to separate major part of sediment from the main channel flow in order to provide required sediment-free water discharge for run-off river hydropower plants. Basically, in the design of Tyrolean weirs, the main concern is to divert at least the design discharge of the facility while it permits to enter the minimum amount of bed-sediment to the system. In this study, water and sediment capture rates of Tyrolean type water-intake structures were investigated for a wide range of discharges by changing the values of some important parameters such as the length of the rack bars, angle of inclination of the rack, the distance between the rack bars, main channel discharge and total amount of sediment. For this reason, a series of experiments were conducted in a model of Tyrolean water-intake structure existing at the hydromechanics laboratory of the Middle East Technical University in order to measure the amount of water and sediment captured by the rack. In the first step of the experiments, optimum rack angle maximizing the amount of water entering the system was determined by testing two different rack angles. Then, the experimental results were compared with the ones obtained from the numerical model constructed on FLOW-3D software to check the consistency of the results. As the second step of the experiments, sediment capture rates of the racks with different properties were tested. The results of these studies were analyzed with those previously obtained from the same model for different rack angles by Yılmaz (2010) and Şahiner (2012) and it was concluded that the most efficient conditions being satisfied when the angle of rack inclination was between 22° and 25°. Dimensional analysis was applied to the relevant variables and the variations of the dependent dimensionless terms with independent dimensionless parameters were plotted in order to prepare design charts for Tyrolean weirs. For a known geometry and main channel discharge, the diverted discharge can be calculated or a proper geometric design can be made to provide the expected discharge to the facility by these diagrams. These charts are valid for the range of the tested data.


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Citation Formats
A. B. Melek, “Determination of optimum rack angle of tyrolean type water-intake structures,” M.S. - Master of Science, Middle East Technical University, 2017.