Performance analysis of a HAT tidal current turbine and wake flow characteristics

• The tidal current power turbine is designed by blade element theory.
• Chord length and twist angle are calculated considering tip loss.
• The performance of turbine is analyzed with various factors.
• Wake velocities behind the designed turbine are calculated by CFD.
• The pattern of wake propagations is compared with theoretical wake model.

Having very strong current on the west coast with up to 10 m tidal range, there are many suitable sites for the application of tidal current power (TCP) in Korea. The turbine, which initially converts the tidal energy, is an important component because it affects the efficiency of the entire system. To design a turbine that can extract the maximum power on the site, the depth and duration of current velocity with respect to direction should be considered. To extract a significant quantity of power, a tidal current farm with a multi-arrangement is necessary in the ocean. The interactions between devices contribute significantly to the total power capacity. Thus, the study of wake propagation is necessary to understand the evolution of the wake behind a turbine. This paper introduces configuration design of horizontal axis tidal current turbine based on the blade element theory, and evaluating its performance with CFD. The maximum efficiency of the designed turbine was calculated as 40% at a tip speed ratio (TSR) of 5. The target capacity of 300 kW was generated at the design velocity, and the performance was stable over a wide range of rotating speeds. To investigate the wakes behind the turbine, unsteady simulation was carried out. The wake velocity distribution was obtained, and velocity deficit was calculated. A large and rapid recovery was observed from 2D to 8D downstream, followed by a much slower recovery beyond. The velocity was recovered up to 86% at 18D downstream.