Abstract
Tidal turbine performance is strongly influenced by surrounding flow conditions, particularly the size and proximity of downstream structures. This study investigates the effects of the size and position of a downstream cylinder, representing a centrifugal reverse osmosis (CRO) module, on turbine performance and wake recovery. Transient computational fluid dynamics simulations are validated against experimental turbine performance and PIV velocity data without a downstream cylinder. Turbine performance is found to be Reynolds independent above 4 × 106 at the turbine's design point. The interaction of turbine flow and blade-induced vortices with the cylinder front is revealed through vorticity contours. Increasing the cylinder diameter or reducing the turbine-to-cylinder distance decreases turbine performance and expands the recirculation region. Larger recirculation zones enhance wake recovery via increased entrainment. For a cylinder-to-turbine diameter ratio of 0.3 and a spacing-to-turbine diameter ratio of 0.1, the cylinder reduced power and thrust by 20.3 % and 12.7 %, while improving wake recovery at x/Dt = 6 from 53 % (no-cylinder case) to 64 %. The cylinder reduced the pressure difference across the turbine, indicating decreased energy extraction capacity.