Numerical Study on the Vertical-Axis Tidal Current Turbine with Coupled Motions (Part I)

Xu, G.; Li, H., and Wang, S., 2019. Numerical study on the vertical-axis tidal current turbine with coupled motions (Part I). In: Hoang, A.T. and Aqeel Ashraf, M. (eds.), Research, Monitoring, and Engineering of Coastal, Port, and Marine Systems. Journal of Coastal Research, Special Issue No. 97, pp. 273–288.With the floating platforms, the vertical-axis tidal current turbine has a multi-degree of freedom motion in the sea. The hydrodynamic performance of the rotated turbine with two (i.e. surge and sway) degrees of freedom in unbounded uniform flow is studied with the dynamic mesh in this work and the turbine for another surge and yaw motion has been published on Ocean Engineering. The effects of the hydrodynamic loads have been studied and illustrated considering the 3-DOF coupled motion (Rotation of turbine, surge and sway motion). Numerical results show that the surge motion mainly causes the effects of the hydrodynamic loads, but the effects of the sway motion will be come out when its frequency is greater than that of the surge. There are fluctuations in the envelope curves of the hydrodynamic loads of the turbine, and the fluctuation amplitudes have a positive relation with the surge and sway motion frequencies. Then the mathematical model of the turbine with 3-DOF coupled motion is established. The results of the hydrodynamic loads calculated by the above model and the numerical simulation executed by CFD (Computational Fluid Dynamics) show good agreements, which verifies the mathematical model. The results of this study can provide reference for the hydrodynamic analysis of turbines with multi-degree of freedom motion.