A modular multibody aeroelastic framework for offshore wind turbines

This work presents a modular two-way multibody-based aeroelastic formulation for offshore horizontal-axis wind turbines. An extended Blade Element Momentum Theory aerodynamics, able to capture inflow-angle variations, wake skewing and platform-motion-induced effects, is interfaced to a structural solver that represents each blade as a chain of spanwise-discretized generalized beam elements. Within the Simulink/Simscape-Multibody™ framework, beam elements are connected by rotational joints describing flapwise, lagwise, and torsional motions, yielding an efficient, dynamically consistent representation of blade flexibility. The resulting body-chain dynamics is governed by the Maggi equations expressed in an inertial frame, where small relative rotations at each joint accumulate to reproduce potentially large global deformations (if any). Drawbacks and advantages of the proposed approach are evaluated using two wind turbines of increasing size – the NREL 5 MW and the IEA 15 MW – in both bottom-fixed configurations under various operating conditions, and floating configurations with prescribed platform motion. Detailed comparisons with established aeroelastic solvers, largely used in the wind-energy community, highlight capabilities and boundaries of the formulation, with particular attention to the role of Blade Element Momentum aerodynamics for aeroelastic purposes, which remains widely adopted in industrial applications. Numerical results show a greater influence of the aerodynamic modeling on simulation accuracy than the specific structural representation used, and the very good agreement with aerodynamic and aeroelastic predictions coming from higher-fidelity solvers, whenever design and weakly off-design conditions are encountered. For both bottom-fixed and floating turbines, a dedicated discussion of performance and elastic blade displacements is provided throughout the paper, linking the numerical behavior to the underlying physical phenomena associated with each operating condition to enhance understanding of the system response. Validation studies herein addressed make the paper a robust benchmark suitable for industrial use in early-stage wind turbine design.