Re-aeration in skimming flow over stepped chutes: two-dimensional CFD modeling and empirical equations

Reaeração em escoamentos deslizantes sobre turbilhões em vertedouros e canais em degraus: modelagem via CFD e proposição de equações empíricas

ABSTRACT

Flows in stepped chutes and spillways are highly turbulent and have the potential of absorbing and desorbing volatile compounds. The present work aimed to model the interfacial mass transfer in skimming flows using the two-resistance model and the advection-diffusion equation. The simulation was conducted in 2D, with two multiphase eulerian models. An empirical formulation is also proposed for predicting the reaeration efficiency in skimming flows with slopes of 45°, 21.8° and 11.3°. The results obtained with the homogeneous and inhomogeneous multiphase models showed behaviors similar to the experimental data by adjusting the global mass transfer coefficient of the two-resistance model and the turbulent Schmidt number, with values in the ranges of 0.0015 to 0.01 m/s and 1 to 5, respectively. The proposed empirical equation resulted in high correlation coefficients and adherence to the experimental data.

Keywords:
Computational fluid dynamics; Mass transfer; Oxygen transfer; Stepped spillways