Numerical studies of wind effects on energy performance of a vessel in following seas, comparing with full-scale measurements

• A complete, 6DoF, reduced fidelity, numerical model that couples irregular wave excitation with time-dependent, dynamic wind loads is developed and validated to simulate vessel behaviour in stern-quartering seas. • Wind gusts are shown to excite yaw resonance and increase rudder activity required for course-keeping, particularly under stern-quartering wind-wave conditions. • It was seen that when combined with an appropriate speed controller, wind in following seas can reduce power consumption. • A CFD-based correction approach is introduced to account for ship-induced flow distortions around onboard wind sensors. • Empirical Mode Decomposition is implemented to investigate the non-stationary dynamic response time series, which was able to isolate wind-driven, high-frequency oscillations and revealed wind as a second-dominant contributor alongside wave excitations. This study presents a numerical investigation into ship dynamics in stern-quartering seas, emphasising the coupled effects of astern wind and wave disturbances. A modular 6DOF manoeuvring model is implemented with dynamic wind loads derived from the Kaimal turbulence spectrum and wave forces derived from linear potential theory. A rudder-based autopilot provides course-keeping, and an RPM controller regulates propeller thrust. The framework is validated against full-scale measurements, showing close agreement in vessel motions and wind behaviour. Results show that wind loads can influence hydrodynamic responses, particularly amplifying yaw resonance and increasing rudder deflections for effective course-keeping in stern-quartering seas. For the studied cases, including wind reduced delivered power, and applying the RPM controller produced additional reductions in required power (combined effect up to 10%). Empirical Mode Decomposition (EMD) analyses of non-stationary time series data further revealed that wind effects can emerge as a significant contribution alongside wave excitations, influencing the vessel’s oscillatory behaviour in yaw and rudder responses. A linear stability assessment with varying wind speeds and autopilot gains further quantifies the directional stability margins. Finally, addressing the uncertainty with wind measurements due to the vessel’s superstructure, a CFD-based correction is proposed to improve the accuracy of wind force calculations and power predictions.