Physical and numerical analysis of flow characteristics in dam spillway structures

In the last 60 years, especially in the last 30 years, great progress and innovations have emerged in the hydroelectric sector in terms of the development of water resources, and in parallel, large hydroelectric projects have been built in the world. Characteristics of large and complex structures that generate hydroelectric power are mainly; high head, large discharge, per unit discharge and complex geological conditions. Dissipating and absorbing such high power generating potential energy, which can be as high as tens or hundreds of gigawatts, is of course one of the most difficult issues of dam engineering. Therefore, considering the hydraulic characteristics of the discharge structures of the dams and the safe and economical distribution of the resulting energy, physical modeling, prototype experiments and numerical modeling results should be evaluated together for an effective project design. Although the physical model method used to evaluate the performance of discharge structures has been successful in the past and today, it is known that the CFD method offers various advantages over physical modeling. Engineering designs in the field of hydraulics to be made today require the use of CFD (Computational Fluid Dynamics) software together with experimental studies. Because the use of such programs in the design of many hydraulic structures will ensure that there are fewer mistakes in planning, and that it will be done in a shorter time and more economically. In this study, the hydraulic characteristics of the discharge structures determined by physical model studies and the efficiency of the energy-absorbing structures were investigated numerically by the CFD method. In the numerical modeling of the study, Flow3D, a successful software, was used to solve problems such as open channel flow, sediment transport, and scour, and water surface pressure values and velocity profiles obtained from numerical calculations were evaluated. In this comparison, the performance of the numerical analysis method was evaluated using physical model test measurements. In the comparison between physical and numerical analysis, the most strong factor affecting the hydraulic characteristics is the air-water relationship, as well as the scale issue is one of the factors affecting the flow. For this reason, the effect of air entrainment on the flow was tried to be determined by running the air entrainment model in the numerical analysis program. In addition to the 1/100 scale physical model of 1982, the results of the 1/30 scale physical model, which was carried out in the same year and only focus on the characteristics of the spillway discharge channel, were added to the results of the same scaled numerical model and other scaled numerical models, and the scale effect was examined in more detail. Again, within the scope of our interest study, 15 different flip buckets have been designed by considering the different deflector angles and Radius, which is one of the effective structures in terms of energy dissipation at the end of the existing spillway structure, and these designs were made and a performance evaluation was made in terms of spillway structure and energy dissipation.