Energy Loss Characterization in Stepped Spillways: Experimental Study and Model Development for Slopes of 8.9°–26.6°

Abstract

Stepped spillways are structures built across dams to lessen the kinetic energy that could create scour at the natural riverbed below it. These structures utilize their stepped design to manage the energy in floodwaters. Numerous studies have point out the damaging effects of the kinetic energy from falling water on the riverbed beneath the structure, particularly with channel slopes exceeding 26.6 degrees. However, few studies have examined the energy loss caused by flat stepped spillways with channel slopes between 26.6 and 8.9 degrees. There is a knowledge gap in the design requirements for flat stepped spillways within these specific channel slopes. The present model to predict energy dissipation in flat stepped spillways incorporates a parameter known as the friction factor, f, which is difficult to estimate and often requires subjective assessment by those who design stepped spillways. This research aims to offer design guidelines for flat stepped spillways, which feature varying slopes of 26.6 degrees and 8.9 degrees, and to substitute the problematic friction factor, f. Experiments were done in big facilities employing phase-detection intrusive probes on flat stepped spillways with channel slopes ranging from 26.6 to 8.9 degrees. This paper presents a model for assessing energy losses in flat stepped spillways with slopes of 26.6 and 8.9 degrees under transitional and skimming flow conditions. The outcomes from the new model correlated well with the measured data, displaying high correlation coefficients between 0.79 and 1.00. All the findings were consistent. The model is user-friendly and provides superior results compared to the previous model.