CFD analysis of bottom-inlet spillway aerators

ABSTRACT PhD Thesis CFD ANALYSIS OF BOTTOM-INLET SPILLWAY AERATORS Mehmet Cihan AYDIN Firat University Graduate School of Natural and Applied Sciences Department of Civil Engineering 2005, Page: 141 Spillways for medium and high-head dams may be exposed to high velocity flows and the associated destructive phenomenon of cavitation. A conventional method to prevent cavitational erosion in high-velocity flow is achieved by aerator devices. The development of spillway aerators has been pioneered to very large extent through the use of physical hydraulic models. But, advanced numerical models have got importance against physical models with recently developing computational methods. In the first parts, a detailed review of the literature for spillway aerators is presented to provide a background for this study and to be useful as a resource for spillway design practitioners. Later, the results of the CFD (Computational Fluid Dynamics) analysis for the spillway aerators are compared to physical model and prototype data presented by other investigators. The results of CFD analysis fairly agree with prototype data, but they do not naturally with physical model data included considerable scale effects. So, the using and efficiency of the CFD models in hydraulic applications like this are discussed. The last, the first time in this thesis, a new aerator type called as "Bottom-inlet Aerator" is suggested in order to prevent submerged aerator condition and to provide a better aeration performance and more uniform air mixture than classical aerators, even for low Froude numbers and wide spillway chutes. For determination of the performance of this aerator, data analysis is performed by using three-dimensional CFD models with Fluent software, and some useful relations are obtained with high correlation. Keywords: Spillway, aerator, cavitation, air entrainment, scale effect, submerged aerators, Fluent, CFD, bottom-inlet aerators. XV