Numerical Modelling of Hydraulic Flow in Dam Stepped Spillway and Study of Cavitation Phenomenon

Cavitation is a phenomenon leading to damaging surfaces and usually occurs at steep and fast overflows. This can be prevented via decreasing pressure upon the floor of overflows or controlling the flow rate. Furthermore, controlling this phenomenon comes about through increasing air concentrations in the overflow. One of the methods of increasing air concentrations and decreasing the flow rate of the spill is to construct overflows in stepped forms. Dam spillway releases are from among shoot overflows which would confront cavitation phenomenon. This research tries to control this phenomenon via constructing stepped spillways instead of installing aeration systems. Because laboratory models and field researches are costly and time-consuming, using numerical modelling via CFD method for designing and simulating hydraulic flows are suggested. In this research, stepped fast flowing dam releases were designed instead of spillway fast flows, and then simulating flows on spillways, the cavitation phenomenon was studied and evaluated. Results from these simulations show that constructing stepped forms upon dam spillway releases are effective in controlling cavitation phenomenon, so that via reducing flow rate and increasing cavitation index, prevention of this phenomenon becomes possible