Viscous Damping Identification for Oscillating Surge Wave Energy Converters: PQ Method and Fourier Series Method

Presenter: Md Riasat Morshed Khan, Mechanical Engineering

Authors: M. Khan, M. Jiang, D. Tafti

Abstract: The design of marine renewable energy converters has advanced from hydrodynamic analysis to optimization and control engineering problems. Potential flow theory-based framework is often the preferred modeling approach for its computational efficiency, despite its limitations in near resonance conditions. Since resource-intensive approaches like Computational Fluid Dynamics (CFD) cannot be integrated into real-time control or optimization solver, a computationally inexpensive, yet accurate alternative is necessary. A non-linearity omitted by low-fidelity modeling, particularly significant for Oscillating Surge Wave Energy Converters (OSWEC), is viscous damping. This study employs the PQ and Fourier Series methods to identify viscous damping coefficients from CFD simulations conducted in OpenFOAM. Incorporating these identified damping coefficients into a time-domain equation of motion significantly improved the accuracy of predicted device rotations, providing results comparable to the CFD data, where potential flow theory alone yielded inaccurate predictions. The derived coefficients offer a computationally efficient means to accurately estimate OSWEC response, enabling their integration into control algorithms and optimization subroutines for devices with similar geometries.