Numerical investigation of simultaneous effect of end sills and roughness on flow characteristics in V-shaped stepped spillways

The special configuration of V- shape stepped spillways increases energy dissipation and aeration compared to the smooth spillways due to the creation of many vortices near the steps. In this research, the energy dissipation in different types of stepped spillways with various horizontal face angles has been investigated using numerical modeling. The FLUENT, was used to model the flow over V-shape stepped spillway. The k-ɛ realizable turbulence model was selected to model the turbulent flow. The numerical results were compared with the available experimental data. The results showed a reasonable agreement between two sets of data. Then the effects of horizontal face angle, roughness and the efficiency of the end sill were investigated by numerical modeling. According to the model results, as the horizontal face angle increased, the energy dissipation also increased. Furthermore, the efficiency of end sill on the stepped spillways increased the rate of energy dissipation about 2.8 to 3.99 percent because the end sill acted like a stilling basin. Moreover, the energy dissipation increased slightly about 0.9 to 1.94 percent by increasing the roughness. Also, areas of steps under the negative pressure that could create cavitation were determined to define the minimum negative pressure and its location in all of models. Finally, the simultaneous effect of several parameters was considered to increase the energy dissipation and the minimum negative pressure.