Coupled aero-hydro-mooring dynamic analysis of floating offshore wind turbine under blade pitch motion

Based on linear potential flow theory, this study investigates the hydrodynamic performance of a co-located farm with an array of floating offshore wind turbines (FOWTs) and floating photovoltaics (FPVs). In this process, to evaluate the wave–structure interaction, domain decomposition and matched eigenfunction method are applied to address the boundary value problem for a complex-shaped co-located farm, and the velocity potential can be decomposed into radiation and diffraction problems. Under the framework of linearized theory, we establish the coupled motion equations by modeling rigid and articulated constraints to evaluate the kinematic response of the FOWTs and FPVs in the co-located farm. For such a system, a co-located farm consisting of an array of OC4-DeepCwind FOWTs and FPVs is proposed and investigated in this study. After running convergence analysis and model validation, the present model is employed to perform a multiparameter effect analysis. Case studies are presented to clarify the effects of solar platform geometric parameters (including column depth, thickness, radius, and total draft), articulated system, and shadow effect on the hydrodynamic behavior of wind and solar platforms. The findings elucidated in this work provide guidance for the optimized design of FPVs and indicate the potential for synergies between wind and solar energy utilization on floating platforms.

Analytical study on hydrodynamic performance of co-located offshore wind–solar farms

Zhu,

Shi,

Tao

et al. 2024

Dynamic responses of a semi-submersible wind turbine platform subjected to focused waves with viscous effects

Yang,

Zhang,

et al. 2024

In most previous studies on the dynamic responses of floating offshore wind turbines, regular wave conditions are assumed in the analysis with the inviscid flow theory. The focused waves, however, have not been considered even though they may have larger wave heights and more concentrated energies, in general, to cause more significant responses in a floating platform. In this study, the characteristics of the dynamic responses of a semi-submersible wind turbine platform subjected to focused waves are studied using a sliding mesh technique with the three-dimensional shear stress transport k–ω turbulence model. Effects of wave steepness, fluid viscosity, and wave nonlinearity on the dynamic responses are investigated. The high-order wave loading in the transverse direction is found significant under high wave steepness conditions. The viscous effects of fluid notably aggravate the pitch and surge dynamics of the floating platform compared to those from under the inviscid flow conditions. Due to the nonlinear characteristics of the focused wave, the floating platform is found to experience a long vibration period and slow drift dynamics in the surge direction after the focused time with significant fluctuation.

An analytical model for estimating aerodynamic damping of wind turbines in the shutdown state

Long,

Jiang,

Huang

et al. 2024

As wind farms are constantly being constructed, the risk of tower failure for wind turbines increases significantly under strong winds. Compared with the extensively concerned wind-induced behaviors during the operating state, those ones during the shutdown state attract little attention but may lead to serious problems of damages or even collapse. To clearly grasp the aero-structure interaction in the shutdown state, this paper develops an analytical model for estimating aerodynamic damping of wind turbines. In this method, an analytical expression of aerodynamic damping coupling matrix is derived via the combination of multibody dynamics and first-order Taylor expansion. This matrix is further quantified as the ratio of modal aerodynamic damping with the aid of state-space equation and complex eigenvalue analysis. This treatment can facilitate the straightforward application of efficient calculation methods, such as frequency domain analysis and uncoupled analysis. More importantly, the developed model is able to simultaneously consider multiple realistic factors, such as blade flexibility, tower top rotation, yaw error, wind shear, and pitch angle. This model may have the high calculation efficiency and accuracy, as well as strong applicability for estimating the aerodynamic damping. Numerical examples based on a typical 5 MW wind turbine are employed to validate the effectiveness of the developed model. Experimental analyses demonstrate that this model outperforms the existing formula and presents a high consistency with OpenFAST in the estimation of aerodynamic damping. Meanwhile, the influence of multiple realistic factors is quantitatively analyzed, which even makes the estimation error exceed 70%.