Author(s): Amir Ghaderi; Saeed Abbasi; Silvia Di Francesco; Rasoul Daneshfaraz; Mirali Mohammadi

Linked Author(s): Saeed Abbasi, Silvia Di Francesco

Keywords: Stepped spillways; Notched on the pool configuration; Energy dissipation; Inception point; Physical model

Abstract: Spillways are commonly constructed as floodwater release facilities in reservoir dams to transfer high energy water. Steps on a stepped spillway play an important role in improving energy dissipation due to the artificial roughness of the steps. This study aims to consider the influence of geometric characteristics of pooled steps on the energy dissipation performance, residual head, flow patterns properties and Darcy roughness coefficient. The localization of inception point of air entrainment is also assessed. For that purpose, different configurations and type (height and notch) are taken into account under various hydraulic conditions at different flow regime. The results showed that the flat step configuration have the best energy dissipation performance as compared with other configurations. Pool element on the steps causes some instabilities on the center axis and sides of the steps, leading the inception point to be moved upstream of the stepped spillway. With notched on the pool elements, their performance is improved; for example, compared with the simple pooled stepped spillway, the amount of energy dissipation and Darcy roughness coefficient increases 7.33% and 8% respectively. The observations exhibited that the notched stepped configurations might reduce however some flow instabilities compared to pooled stepped configurations. Although more research is necessary on the topic, the present work shows that the modified notched step configuration is the best choice for pooled stepped designs.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221432

Year: 2022