Numerical validation of novel scaling laws for air entrainment in water

Abstract

The Froude scaling laws have been used to model a wide range of water flows at reduced size for almost a century. In such Froude scale models, significant scale effects for air–water flows (e.g. hydraulic jumps or wave breaking) are typically observed. This study introduces novel scaling laws, excluding scale effects in the modelling of air–water flows. This is achieved by deriving the conditions under which the governing equations are self-similar. The one-parameter Lie group of point-scaling transformations is applied to the Reynolds-averaged Navier–Stokes equations, including surface tension effects. The scaling relationships between variables are derived for the flow variables, fluid properties and initial and boundary conditions. Numerical simulations are conducted to validate the novel scaling laws for (i) a dam break flow interacting with an obstacle and (ii) a vertical plunging water jet. Results for flow variables, void fraction and turbulent kinetic energy are shown to be self-similar at different scales, i.e. they collapse in dimensionless form. Moreover, these results are compared with those obtained using the traditional Froude scaling laws, showing significant scale effects. The novel scaling laws are a more universal and flexible alternative with a genuine potential to improve laboratory modelling of air–water flows.

Numerical investigation of dam break flow over erodible beds with diverse substrate level variations

“…There is a consensus that the flow turbulence in dam break wavefront differs significantly from steady boundary layer flow (Catucci et al, 2021;Khoshkonesh et al, 2023). In cases where the flow dynamics and sediment transport vary rapidly over time, transient or unsteady flow models may be more suitable for accurate predictions (Dodangeh and Afzalimehr, 2022).…”

Exploring the Sensitivity of the Transient Response following Power Failure to Air Valve and Pipeline Characteristics

“…Research relating to air in pressurised pipelines can be categorised into three classes: experimental studies [16], combined experimental-numerical investigations [17], and purely numerical explorations [18]. Due to space limitations in controlled labs, experimental and experimental-numerical studies often focus on small-scale systems, which hinders their applicability to large-scale applications [19]. For instance, although the Bergant et al (2012) study [20] conducted an experimental-numerical investigation using typical air valve and pipe sizes, the pipeline lengths employed were quite short.…”