Impact of Downstream Centrifugal Reverse Osmosis Module on Tidal Turbine Performance*

This study investigates the performance of tidal turbines with downstream Centrifugal Reverse Osmosis (CRO) module through Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations. Mesh independence study is conducted with mesh sizes of 6 million (6M), 10 million (10M), and 17 million (17M) cells by comparing the power coefficient (Cp) and thrust coefficient (Ct) of the turbine. The difference in Cp and Ct  between the 6M and 17M cases is approximately 3%, while the difference between the 10M and 17M cases is around 1%, leading to the selection of the 10M mesh for further simulations. The simulations employing the k-ω SST turbulence model are validated against laboratory experiments (1:20 scale) without the CRO module downstream. The same mathematical and numerical models are adopted for the full-scale tidal turbine simulations. The study explores the influence of the CRO module's diameter, varying between 0.1D_t and 0.5D_t (where D_t is the turbine diameter of 5.5 meters), and the module’s axial position from the rotor, ranging between 0.25D_t and 1D_t. This comprehensive analysis aims to enhance the understanding of the interactions between tidal turbines and downstream flow modifications, contributing to the shape and position optimization of downstream objects.