Investigation of aero-hydro-elastic-mooring behavior of a H-type floating vertical axis wind turbine using coupled CFD-FEM method.

Floating vertical axis wind turbines (VAWTs) are being explored as a promising new option for harnessing offshore wind energy due to their unique advantages, including low installation and maintenance costs, high operational efficiency in wind farm clusters, and scalability of rotor sizes. However, the lack of software capable of simulating the aeroelastic of VAWTs poses a significant barrier to their further development and deployment. The aim of this paper is to develop a fully coupled aero-hydro-elastic-mooring-material model for floating VAWTs. The aerodynamic performance, hydrodynamic response and structural nonlinearities of the floating VAWT are analyzed in detail using Computational Fluid Dynamics (CFD) and the Finite Element Method (FEM). The results indicate that: (i) The dynamic response of the floating VAWT platform results in more pronounced fluctuations in the power coefficient, characterized by frequent spike-like extreme values, compared to fixed VAWT. Nevertheless, wake dissipation in floating VAWT is quicker, facilitating faster flow recovery and a more marked acceleration effect in the flow field. (ii) The surge and pitch motions of the platform affect the velocity of the blades relative to the fluid, resulting in additive and subtractive effects with the incoming flow. This interaction gives the blade torque of the floating VAWT an alternating performance advantage in the upwind region, compared to fixed VAWT; (iii) Stress analysis reveals that the highest levels of stress occur at the juncture between the support arm and the blade, with significant stress also present at the bottom of the central pontoon. In contrast, the blade tips exhibit the lowest stress levels. (iv) The blades of the floating VAWT undergo radial deformation due to wind loads and centrifugal forces, while the support arms experience vertical vibrations, driven by their own weight combined with that of the blades. (v) The mooring lines, particularly influenced by platform traction and frequent interactions with the seabed, show dynamic shifts in maximum contact pressures, especially between moorings C2 and C3. Mooring C2, located on the windward side, consistently faces more intense seabed interactions.