Lateral force fluctuation on the shaft of vertical-axis ocean current turbine

Lateral force fluctuation on the shaft of fixed and passive variable pitch vertical-axis ocean current turbine in unidirectional and perpendicular with the fluid flow (Fx and Fy) have been studied. A vertical-axis turbine system consisting of shaft and three straight foils as a producer of force which obtained through the CFD simulation using rotation data test results from towing tank. Variations of incoming fluid velocity and the corresponding rotation velocity were used to identify the pattern of lateral force fluctuation. Investigation of Fx and Fy fluctuations showed periodic pattern and increases with U. Shifting patterns of Fx and Fy on a foil produced with the use of passive variable pitch following the angle of freedom 10⁰ given. Changes in pattern of force occurred in the area of azimuth rotation of 20⁰<θ<40⁰, and contributes to avoiding the occurrence of stall, as well as improve the ability to self-start on the vertical-axis turbine. The resulted fluctuating direction of F-res vector as a resultant of Fx and Fy in the use of fixed pitch turbine in quadrant system is -15⁰<ß<20⁰, while the F-res vector on passive variable pitch produces a fluctuating direction of -5⁰<ß<20⁰. According to the pitch angle of freedom, comparison of angle F-res vector area of passive variable pitch to pitch fixed type showed a reduction of ß of ±10⁰. Periodization of Fx and Fy fluctuation pattern in a vertical-axis turbine correlated to the distance between the foil and the n-foil used, and not influenced by variations of the pitch type used.