Abstract
The TidGen 2.0 Power System is an electricity generation system which functions by harnessing energy from tidal currents. The current work looks to assess the hydrodynamic characteristics of its buoyancy assembly using computational fluid dynamics. The numerical simulation is performed using a transient k-epsilon Reynolds-averaged Navier-Stokes numerical scheme. The main set of simulations was done with a simplified geometry model consisting of an elongated cylindrical form. Variation in flow attack angles was simulated to represent system pitch at the prevalent operational current flow speed. Its effect on the lift coefficient was monitored to ensure the buoyancy assembly is not susceptible to periodic vortex shedding, which is a pre-cursor to vortex-induced vibrations (VIV). VIV would negatively impact component structural strength and fatigue life. The simplified geometry simulations show in-line drag to be low in the range 0.28 to 0.31 for the 0 to 5 deg. attack angle considered. However, vortex shedding was seen to be periodic which may present a VIV risk. Therefore further investigation was performed using a more detailed buoyancy assembly model with surface features like flanges and corrugations. It was shown the base in-line drag coefficient increased from 0.28 to 0.36. The VIV propensity was assessed to be adequately mitigated and not be a significant concern. Overall, the in-line drag is shown to be suitably low with minor risk of VIV occurring and is deemed suitable for the purposes of the TidGen 2.0 system implementation.