Session: 16-01-01 Offshore Wind Energy and Renewables

Submission Number: 175402

Numerical Investigation of Coupled Dynamics and Energy Performance in Hybrid Floating Offshore Wind Turbines With Integrated Oscillating Water Columns 

The integration of floating offshore wind turbines (FOWTs) with oscillating water column (OWC)-based wave energy converters offers a promising avenue for enhancing the efficiency and resilience of ocean energy systems. This study presents a comprehensive numerical investigation of two configurations: a reference semi-submersible FOWT and a hybrid floating offshore hybrid wind turbine with integrated OWCs (FOHWT-E). The central objective is to evaluate the coupled aero-hydro-servo-elastic behavior of these systems and to quantify the implications of OWC integration on platform motions, structural response, and overall energy conversion. The methodology combines multiple modeling frameworks to achieve a consistent and rigorous representation of the coupled dynamics. Aerodynamic loads are resolved through Blade Element Momentum (BEM) theory, while hydrodynamic forces are modeled using linear potential flow theory supplemented by viscous corrections via Morison elements. The OWC chambers are represented through a thermodynamic formulation of the air chamber dynamics coupled with an impulse turbine model, ensuring that both hydrodynamic and pneumatic interactions are captured. The floating platform is modeled with six degrees of freedom, allowing full representation of rigid-body motions and their interaction with aerodynamic and hydrodynamic loads. The analysis proceeds across complementary domains. Hydrostatic calculations provide initial stability metrics, followed by frequency-domain characterization through added mass, radiation damping, and response amplitude operators (RAOs). These are further supplemented by free-decay simulations to estimate natural periods and damping properties. Fully coupled time-domain simulations are then conducted under irregular wave conditions, allowing nonlinear effects and multi-physics interactions to be assessed. This multi-level approach ensures that the models are not only internally consistent but also provide a robust framework for cross-domain verification between frequency- and time-domain results. The results demonstrate that the hybrid FOHWT-E exhibits significant performance advantages over the standalone FOWT. From a hydrodynamic standpoint, the inclusion of OWCs enhances stability, more than doubling the metacentric height and substantially increasing hydrostatic stiffness. Pitch motions are attenuated by over 50%, leading to consistently lower tower base bending moments across all tested wind conditions. From an energy perspective, the OWC turbines contribute an additional rated capacity of 750 kW, enabling total power gains of up to 38% in low wind conditions (<6 m/s) and between 7–12% at rated and above-rated regimes. Overall, the study highlights the methodological value of integrating linear and nonlinear time- and frequency-domain approaches for the evaluation of hybrid offshore renewable systems. The findings not only demonstrate the technical feasibility and performance benefits of the FOHWT-E concept but also provide a reproducible modeling framework that can be extended to future multi-purpose floating platforms.

Presenting Author: Gabriel Siqueira Machado GERO

Presenting Author Biography: Bachelor’s degree in Exact Sciences and Mechanical Engineering from the Federal University of Juiz de Fora. Master’s degree in Mechanical Engineering from the Federal University of Rio de Janeiro. Currently a Ph.D. candidate in Ocean Engineering at the Federal University of Rio de Janeiro and a researcher at the Ocean Renewable Energy Group. His research interests include offshore dynamics, aero-hydrodynamics, hybrid wind–wave energy systems, numerical simulation, and coupled modeling approaches. His doctoral work focuses on the development and assessment of hybrid floating offshore wind turbines with integrated oscillating water columns (OWCs), with emphasis on coupled aero-hydro-servo-elastic analysis and the evaluation of system performance under realistic environmental conditions.

Authors:

Gabriel Siqueira Machado GERO
Milad Shadman GERO
Segen Estefen GERO