OpenFOAM vs FLOW-3D: A comparative study of vertical slot fishway modelling

The objective of this study is to make a comparison between two 3D CFD platforms: OpenFOAM (free and opensource CFD software) and FLOW-3D (closed source commercial CFD software), focusing on vertical slot fishways, one of the most widespread solutions to facilitate the fish migration through transversal obstacles in rivers. Considering previous comparative studies, our initial hypothesis is that both OpenFOAMs' multiphase solver and FLOW-3D provide good comparable results. In this study, in contrast to previous comparative studies, turbulence was addressed using LES approach and the volume of fluid method was used to model the multiphase interface (air-water). Mesh independency was assessed through LES IQ index and the numerical models' accuracies were evaluated comparing representative hydraulic variables (velocity, its components, and turbulence kinetic energy) with ADV experimental data and discussing results in previous studies. Both platform codes reproduced the scenario under study, concurred with experimental data and offered a superior performance on flow structure velocity simulation than turbulent kinetic energy. Results validate the use of the free and open platform OpenFOAM as a viable alternative to commercial ones in the domain of fishway design and assessment. While OpenFOAM provides a reliable free alternative, FLOW-3D has a faster setup and makes the simulating experience apt for beginners.