Performance evaluation of a bidirectional horizontal axis tidal turbine with S-shaped blades by the sliced section method

Understanding the flow pressure distribution on the blade airfoil of the tidal turbine is of great significance for optimising the energy harvesting performance of the blades. In this paper, a bidirectional type horizontal tidal turbine (BHTT) with special S-shaped blades is proposed, which have a larger pitch diameter ratio provide excellent performance at low oncoming flow velocity by the theoretical, numerical and experimental methods. First, it is verified that the energy harvesting efficiency is basically the same in the case of bidirectional flow, and the S-shaped blade is divided into multiple slice sections, which could quantify the energy harvesting performance of each area of the blade. Then, using the method of mathematical statistics to divide more areas, the probability density shows a skewed distribution. The results show that the energy harvesting performance is less affected by flow velocity fluctuation, and the energy harvesting efficiency could reach 0.25-0.55 when the tip speed ratio is in the range of 0.2-0.5. Furthermore, the slice section method is adopted to make the influence of axial thrust intuitive and clear to study the turbine energy harvesting performance and improve the harvesting efficiency, which could provide a reference for the engineering design of tidal turbines.