Abstract
In the stepped spillway, the steps, by providing an artificial roughening bed, dissipate the flow of energy more than other types of spillways, so the construction costs for stilling basin are reduced. However, what is important in this type of spillway is increasing the effectiveness of steps in the rate of energy dissipation. The present study deals with experimental and numerical simulations regarding the influence of geometric appendance elements on the steps and its impact on the energy dissipation performances, flow patterns properties, turbulent kinetic energy, flow resistance and the Darcy roughness. The localization of inception point of air entrainment is also assessed. To this aim, different configurations are taken into account. The computational procedure is validated with experimental results and then used to test the hydraulic behavior of different geometric configurations. The results showed that the appendance elements on the steps increased the turbulent kinetic energy (TKE) values and Darcy–Weisbach friction and the energy dissipation increased significantly. By reducing the height of the elements, energy dissipation and the TKE value increase more significantly. With the appendance elements on step, the air entrainment inception locations a positioning further upstream than the flat step stepped spillway.
Highlights
Spillways are one of the best solutions as floodwater release facilities in reservoir dams to transfer high-energy water and dissipate water flow energy as well as to rehabilitate embankment dams [1,2]
Skimming flow is dominant because most prototypes of stepped spillways operate in large discharges and the aeration and energy dissipation performances are well documented for flat uniform stepped spillways with embankment dam slopes and based on studies by Chanson and Toombes [6], Ohtsu et al [7], Gonzalez and Chanson [8], Felder and Chanson [9], Bung [10] and Hunt et al [11]
This study aims to consider the elements appendance on the steps and its impact on characteristics of flow water over the stepped spillway such as flow pattern, energy dissipation and residual head, flow resistance and inception points on the flat and the elements appendance on the steps of the stepped spillway
Summary
Spillways are one of the best solutions as floodwater release facilities in reservoir dams to transfer high-energy water and dissipate water flow energy as well as to rehabilitate embankment dams [1,2]. Based on the mentioned studies and depending on flow conditions, the flow over a stepped spillway is usually categorized into three regimes: nappe, transition, and skimming. The stepped spillway is often designed for skimming flows. Skimming flow is dominant because most prototypes of stepped spillways operate in large discharges and the aeration and energy dissipation performances are well documented for flat uniform stepped spillways with embankment dam slopes (i.e., chute angles from the horizontal between 22◦ and 30◦ ) and based on studies by Chanson and Toombes [6], Ohtsu et al [7], Gonzalez and Chanson [8], Felder and Chanson [9], Bung [10] and Hunt et al [11]
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