The 12th International Conference on Hydrodynamics
18 – 23 september 2016, Egmond aan Zee, The Netherlands
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Go-down ichd2016 Tracking Number 118

Session: Hydrodynamics in Ocean III
Room: Room 3
Session start: 10:30 Tue 20 Sep 2016

Abhay Srivastava
Affifliation: Indian Institute of Technology, Kharagpur

Joydip Bhattacharjee
Affifliation: Indian Institute of Technology, Kharagpur

Topics: - Hydrodynamics in ocean, coastal and estuary engineering


The world oceans are enormous source of renewable energy that has remained largely untapped till date. Among different forms of ocean energy, tidal power is one of the most powerful resources that bears the advantages of high predictability, periodic availability and high concentration of power. India has a long coastline, which is thickly populated following the global trend. Hence, to meet the ever increasing demand of electricity, it has become necessary to exploit the power from tidal current. There are several locations in India including the Gujarat coast in the west and the Sundarbans, West Bengal in the east, where the tidal range is suitable for energy extraction. It is well understood that the tidal current stream generators are advantageous over the tidal barrage systems in terms of both economic viability and environmental concerns. The working principle of tidal current turbines is same as the wind turbines. However, since water is much denser than air, the tidal turbine will give more energy than a wind turbine of same dimension assuming same wind speed as water. Although no particular device has emerged as the preferred one for the industry, out of different variants, vertical axis marine current turbine (MCT) is one of the variant that is being studied to improve the efficiency. Vertical axis MCT rotates about a vertical axis which is perpendicular to the current flow direction. The turbine comprises of a number of blades having hydrofoil sections that are mounted vertically between the top and bottom support. Vertical axis MCT is capable of extracting energy from any incoming direction of the tidal steam, which is not the case for horizontal axis turbine. However, vertical axis MCT shows high torque fluctuations and has no self starting capability. In the present study, an attempt has been made to optimally design a vertical axis MCT. The maximum efficiency is obtained by modifying distinct design parameters that affects significantly the power capture efficiency. The turbine is consisting of five blades, which are being modeled using the selected airfoil section of NACA0021. Airfoil section NACA0021 is selected by considering both the hydrodynamics and robustness of designed turbine. The device is designed for a water depth of 6 m. Hence, considering the effect of cavitation and availing space for machinery, blade length is chosen to be 3 m. To get enough swept area, the diameter of the turbine was chosen to be 5.15 m, giving a swept area of 16 m2. The aspect ratio is defined as the ratio between the water depth and the diameter of the turbine, which is equal to 1.167. Using modified designing algorithm, power coefficient is found to be 0.41 and total extracted power through turbine is found to be approximately 18 KW in the initial numerical computations. The effect of the tip speed ratio, rpm of the rotor, Reynolds number of the flow on the efficiency of the device are studied in detail. The flow passed the device and the surrounding pressure distribution is being studied using ANSYS-CFX.