CFD Analysis of the Flow around the Top Fin of the Flumill Tidal Turbine

Abstract

OpenFOAM is an open-source software suite which is available as a free download. The software is under rapid development, and is gaining a wide user base in both industry and academia. In the current project, OpenFOAM is used on an industrial case, namely the optimization of the design of the top fin on a tidal turbine, with the intent of minimizing vortex-induced vibrations.Two different profiles, the original design and a more streamlined NACA-0033 foil, are taken through so-called alpha-sweeps, slow 180-degree rotations relative to the flow direction, during which the forces on them are recorded. From this information, the profiles' hydrodynamic "signatures" in the time- and frequency-plane are drawn up, and a recommendation is made based on these.In order to validate the computational setup, a series of simulations for a NACA-0012 foil at various angles of attack, and for a circular cylinder, are performed. All the simulations are performed as both two-dimensional URANS-simulations and as three-dimensional DES-simulations, and their results are compared. It's found that the DES simulations don't perform as desired, but that the results from the URANS simulations are capable of filling in the blanks wherever the DES-data is found lacking.