Numerical Simulation of Air Entrainment in Stepped Spillways

FABIAN BOMBARDELLI; FEDERICO ZABALETA; SANTIAGO MARQUEZ DAMIAN

Congreso; 9 th International Symposium on Hydraulic Structures; 2022

Existing methods to simulate air entrainment in stepped spillways are based on a sub-grid air-entrainment function that accounts for the incorporation of air through the air-water interface; a transport equation for the bubbly phase is then solved inside the water domain. Unfortunately, these techniques are unable to represent bulking, i.e., the increase in water depths after the inception point. In this work, we introduce a novel method for the simulation of flow in stepped spillways (including the aerated region). The new air-entrainment model is implemented in the OpenFOAM platform and couples an air-concentration-transport equation with the traditional Volume-of-Fluid (VoF) method to account for bulking. The model was calibrated and validated using the experimental data by Amador (2005) and Felder and Chanson (2013). Air concentration and mean free surface location in the aerated region (defined as where the concentration of air is 90%) are analyzed on the top of the steps as well as inside the cavities. Very satisfactory agreement in the wall-normal distribution of air concentrations between model and experiments was obtained. The model showed to be capable of predicting bulking in stepped spillways, without the need for ad-hoc treatments