Evaluation and sensitivity analysis of three-dimensional numerical simulation for aerated deflector-generated jets in spillways

Abstract

Aeration is an efficient way to prevent cavitation erosion of a discharge structure and alleviate damage to trajectory nappe on the downstream energy dissipator. Due to the complexity of the aeration jet, it is still a big challenge to understand the aeration mechanism at the water-air interface. This study applied the two-fluid model to simulate three-dimensional entrainment characteristics of jet flow, and also analyzed effects of bubble size, wall roughness, drag force model, turbulence model, and numerical model dimension on clear-water length. Results reveal that the two-fluid model can accurately and effectively simulate clear-water length, thickness variation, and average cross-section air concentration of jet flow with maximum error of 4.1%, 6.5% and 4.2% (x = L1, defining clear-water length with 1% air concentration as L1), respectively. Wall roughness height has a crucial influence on clear-water length. Taking L1 as an example, clear-water length decreases by 13.9% when roughness height increases from 0 to 3 mm. The drag models and bubble particle sizes affect clear-water length only when the profile aeration concentration is greater than 15%. Turbulence model and numerical model dimension have a minor effect on clear-water length. HIGHLIGHTS Two-fluid model can accurately simulate aerated deflector-generated jets.; The wall roughness height has a crucial influence on the clear-water length.; The drag models and bubble particle sizes affect clear-water length only when the profile aeration concentration is greater than 15%.; Turbulence model has a minor effect on the clear-water length.;

Keywords

• air concentration
• clear-water length
• multiphase flow
• numerical simulation
• the two-fluid model