Influence of a Modified Weir Profile on Velocity Field and Dissipation Rate in Stepped Spillways: A Comparative Study Using Physical Models and Computational Fluid Dynamics

Abstract

Stepped spillways are specialized hydraulic structures crafted to optimize the effective dissipation of hydraulic energy along stepped chutes. The central objective is to scrutinize and improve the mitigation of flow separation occurring from the ogee crest to the stepped chute, focusing on various profiles within the critical zone (CZ) to understand its flow behavior. The study evaluates the impact of CZ profile alterations on velocity distribution, revealing a reduction in velocity ranging from 10% to 18% for nappe flow and 7% to 15% for skimming flow, with a dissipation rate 5% higher than other tested profiles in the CZ. By combining physical experiments and numerical simulations, the research aims to understand the complex dynamics of CZ flow. A comparative analysis is conducted, comparing turbulence models (specifically RNG) against experimental data for velocity and dissipation rate, considering different numbers of steps (N=16, 22, 56, 60). Moreover, the research seeks to unravel the effects of introducing additional steps within the CZ on crucial hydraulic parameters. The results indicate a significant improvement in flow patterns, velocity fields, and energy dissipation for the modified profile, highlighting the practical applicability of the proposed approaches in effectively sizing the CZ.

Keywords

• spillways
• hydraulic of dams
• stepped spillways
• computational fluid dynamics
• turbulence modelling
• transition zone