Neuro-Fuzzy Approach for Estimating Energy Dissipation in Skimming Flow over Stepped Spillways

In a stepped spillway, the spillway face is provided with a series of steps from near the crest to the toe. The energy dissipation caused by the steps reduces the size of the energy dissipator, generally provided at the toe of the spillway. The hydraulics of stepped spillways is investigated by carrying out laboratory experiments, building models to explain the data, and testing the robustness of the models developed here using a neuro-fuzzy approach. The experiments consist of twenty different stepped spillways tested in a horizontal laboratory flume, a wide range of discharge values, three weir slopes of 15A degrees, 25A degrees, and 45A degrees and different step numbers from 3 to 50 on the ogee surface. The main objective of this paper was to investigate the applicability and accuracy of the neuro-fuzzy approach in estimating the proper values of energy dissipation of skimming flow regime over stepped spillways because of the imprecise, insufficient, ambiguous and uncertain data available. A neuro-fuzzy approach was developed to relate the input and output (energy dissipation) variables. Multiple regression equations based on dimensional analysis theory were developed for computing energy dissipation over stepped spillways. The determination coefficients for the suggested neuro-fuzzy model in training and testing process are 0.974 and 0.966, respectively. It was found that the neuro-fuzzy approach formulation of the problem of solving for the energy dissipation over stepped spillways is more successful than that by regression equations.