Author(s): Arnau Bayon; Mohamed Radwan; Daniel Valero; Mario J. Franca
Linked Author(s): Daniel Valero
Keywords: Gravity current; CFD; RANS; OpenFOAM; K-ε; K-ω
Abstract: Gravity currents are relevant environmental flows, present in maritime and coastal applications, river hydraulics, and atmospheric flows. Their impacts on natural and human systems are substantial provided that they are able to transport large amounts of mass, frequently at large velocities and distances. Computational Fluid Dynamics (CFD) can be a valuable alternative to investigate gravity currents given the intrinsic handicaps associated to quantitative experimental studies. The research herein presented analyzes a contained gravity current using different Reynolds Averaged Navier-Stokes (RANS) models (Standard k-ε, RNG k-ε, k-ω SST, and Launder & Sharma k-ε) on a two-dimensional numerical domain. The model is implemented in OpenFOAM, and its validation is based on a previous laboratory case study. This research reaffirms that gravity current predictions are highly sensitive to the used turbulence model. From all the tested turbulence models, the low-Reynolds number model Launder & Sharma k-ε showed most accurate, capturing the flow behavior even at late stages of deceleration. The sensitivity to the turbulent Schmidt number, reciprocal to the turbulent diffusion, is also analyzed, although it shows moderate impact in this study, probably due to the numerical diffusion caused by the discretization schemes. In conclusion, the computationally-inexpensive RANS models can be used to predict gravity current behavior for most engineering applications.