Abstract
In this research, Flow-3D software uses to study the energy dissipation for stepped spillways with different end sills. The study is bases on three models. The first model contains rectangular end sills in all steppes. The second model contains rectangular end sills between one step and another. The third model contains triangular end sills in all steppes. For each of these models, three different variables are adopt, slope, height of the spillway and a number of steppes, and four different discharges value, carrying the total number of experiments to (324) tests.Analytical results show that the model (3) is the highest energy dissipation for all discharges value. Empirical equations extraction to find the energy dissipation for each of these models. The artificial neural network is also adopt to prove the accuracy and efficiency of the analytical results which are at high rates of compatibility with the values of the coefficient of determination for (model 1), (model 2) and (model 3) equal to (93.47%), (88.20%) and (86.00%) respectively. Also, artificial neural network identifies the most influential factors on the energy dissipation, the friction Froude number is the highest impact on the energy dissipation for models (1) and (2), while the parameter (b/ks) for the model (1).
Highlights
Stepped spillways are considered as hydraulic structures that have a significant effect in reducing erosion at the downstream of dams
Artificial neural network (ANN) and the techniques of gene expression used for modeling the experimental data of nappe and skimming flow over stepped spillways, so the results obtained from these techniques were at a reliable level in the prediction of the energy dissipation [10]
In order to evaluate the accuracy of the analytical model, a comparison is made between the amount of energy dissipation in the experimental results of (Kurukji [17]) and data obtained by Flow-3D for model (1) under the same conditions, Table 1 shows a good degree of compatibility in the results for the different cases of flow over the stepped spillway which including three types depending mainly on the amount of discharge and the geometry of spillway
Summary
Stepped spillways are considered as hydraulic structures that have a significant effect in reducing erosion at the downstream of dams. Based on stepped spillways which have increased surface roughness to increase energy dissipation for various forms of steps, results showed the model with roughness increased the dispersion for both high and low discharge [13,14]. It was based on the special geometry of steps shape for the spillways stepped, labyrinth or quarter circle geometry at step edges, these types of model achieved a percentage of energy gain dissipated [15,16]. Used different configurations on the steps of the spillway and different end sills, which showed the high level of dissipation in different forms from the traditional type, and the elimination of air pockets [17,18]
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