Effect of slope on energy dissipation for flow over a stepped spillway

Abstract

In a stepped spillway, the spillway face is provided with a series of steps from near the crest to the toe. This type of spillway is attractive for water resource management because it dissipates energy that is within the flow. When energy is dissipated by the steps, it reduces the energy reduction that otherwise must occur at the toe of the spillway. In the present study, nine physical stepped spillway models with slopes of 15, 25, 45° and with a number of steps varying from 5 to 50 have been constructed. The crest of the spillways have standard Ogee profiles and a constant slope extends from the crest to the spillway toe. Two different-sized flumes were used in the experiments (25 and 50 cm wide). Several physical models have been constructed in order to measure the energy dissipation. The purpose of this research is to investigate energy dissipation rate in spillways with different slopes. It was found that the two most important dimensionless factors influencing energy dissipation are the Froude number and q2/(gHdam3). The spillway slope and step number have less impact on the rate of energy dissipation. However, for a constant discharge over a stepped spillway, increasing spillway slope, and increasing the number of steps will increase the energy dissipation. Using multiple regressions, some useful relations for determination energy dissipating are obtained. HIGHLIGHTS Energy dissipation rate is investigated in stepped spillways with different slopes.; It was found that the two most important dimensionless factors influencing energy dissipation are the Froude number and q2/(gHdam3).; The spillway slope and step number have less impact on the rate of energy dissipation.; Increasing spillway slope and increasing the number of steps will increase the energy dissipation.;

Keywords

• energy dissipation
• multiple regression
• number of step
• slope
• stepped spillway