Investigation of stepped spillways by computational fluid dynamics (CFD) method

Stepped spillways can dissipate most of the flow energy thanks to the steps placed along the discharge channel. These spillways, which have been used for centuries due to the effect of steps on energy dissipation, have also been the subject of many academic studies. Researchers continue to propose different step geometries in order to achieve better results in the energy dissipation ratio. In this thesis, the flow in stepped spillways was numerically investigated by using Flow-3D, which is one of the Computational Fluid Dynamics (CFD) method software. The study basically consists of two parts. In the first part, the experimental results of Antalya Gökçeler Dam stepped spillway, modeled on 1/40 scale by DSI TAKK Department, were analyzed numerically using four different turbulence models (𝑘-𝜀, 𝑘-𝜔, LES, RNG) and the most compatible turbulence models with the experimental results were determined. In the second part of the study, numerical verification was made using the experimental results of a classical stepped spillway model in the literature and triangular stepped spillway geometries were proposed. As a result of the comparison of the analyses carried out in the first part of the study with the experimental results, it was observed that 𝑘-𝜔 was the most compatible turbulence model for flow rate-levels curves; 𝑘-𝜀 was the most compatible turbulence model for spillway pressure measurements, dissipated energy ratios and approach channel velocities; and LES (Large Edyy Simulation) was the most compatible turbulence model for spillway water surface profiles. As a result of the analyses carried out in the second part of the study, it was concluded that the energy dissipation rate decreases as the flow rate increases in all models, triangular stepped spillways can dissipate more energy than conventional stepped spillways at all flow rates used in the study, the energy dissipation rate increases with the increase in step depth (ht) in triangular stepped models, and triangular stepped spillways can dissipate up to 78% more energy than conventional stepped spillways.