Numerical analysis of labyrinth crested shaft spillway

The spillways, which are the most important hydraulic elements of the dams, are designed in many different types according to the dam type and flow rates. Shaft type spillways, which are one of them, are preferred especially for reasons such as space constraints on the dam body and vibration. Another spillway type, labyrinth type weirs, have more flow rate with the same nappe load. In this thesis, it is aimed to obtain a new type of spillway which is a hybrid spillway type obtained by using these two spillway types together. Thus, the labyrinth crest shaft type spillway type has been developed in which the advantages of both spillways are presented together. For this purpose, the spillway of Kale Dam, which is being constructed on Seyhan Stream in Cermik district of Diyarbakır, was taken as a model. First, the numerical model of this shaft type spillway was analyzed according to the original design. The physical model test results carried out by the State Hydraulic Works (DSI) were used to test the accuracy of the numerical model. Then, considering the same geometrical and hydraulic conditions in the original project, three different trapezoidal labyrinth spillway crests were tested. FLOW-3D program, which is a Computational Fluid Dynamics (HAD) software, was used for numerical analysis on prototype scale. In numerical calculations, the dynamics of real and turbulent flow are realized by the solution of Reynolds Mean Navier Stokes (RANS) equations of motion. As a result of the study, the newly developed labyrinth crest shaft spillway has a much better overflow capacity compared to traditional circular crest shaft spillways. In terms of spillway efficiency, it was found to be more efficient in low nappe loads compared to the classical type, while it was observed that the spillway per unit length decreased at high nappe loads. At the same time, small labyrinth peak angles with high flow rates need to be considered for cavitation. In the light of the results obtained from this thesis, it can be said that the new design developed will provide a better alternative for dam engineering by providing a more efficient reservoir operation and also the HAD method used is very effective in the design of such hydraulic structures.