Modelling of oscillating foil propulsors in waves

• Published in: Ocean engineering 2023-01, Vol.268, p.113316, Article 113316
• Main Authors: Lopes, D.B.S., Vaz, G., Falcão de Campos, J.A.C., Sarmento, A.J.N.A.
• Format: Article
• Language: English
• Subjects: CFD; Hydrofoil modelling; Oscillating hydrofoils; ReFRESCO; Thin-wing theory; Wave propulsion
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2022.113316

This study addresses the possibility of extracting energy from gravity waves for marine propulsion by an oscillating hydrofoil. Moreover, it investigates theoretical and numerical methods to achieve modelling of active oscillating wave thrusters. The first part of this work presents a semi-analytical model based on an extension of classical theory of a 2D unsteady hydrofoil, with large oscillations, in waves, including free-surface effects. The second part investigates the same problem with numerical modelling using a CFD solver. Specifically, a deforming grid method is used for body motion modelling, enabling the simulation of cases with large forced motions. The results of the semi-analytical model for mean thrust and propulsive efficiency are compared with published numerical and experimental data, with fair-to-good agreement. The results of CFD simulations for 2D and 3D test cases are investigated, allowing physical interpretation of flow dynamics and forces. Preliminary comparisons with published numerical and experimental results show a promising good agreement. The overall results suggest that the semi-analytical model may prove its usefulness in preliminary design studies, and the CFD model showed itself to be a tool capable of delivering more accurate results for the most complex cases and providing a comprehensive understanding of the flow dynamics. •Theoretical and numerical modelling combination demonstrated to be effective in investigating oscillating foil in waves's parameter space.•Classical unsteady thin-wing theory can be enhanced to study oscillating foil propulsor with free-surface and incident waves.•ReFRESCO CFD solver proved to be highly suitable to investigate the hydrodynamic problem of the oscillating foil propulsor.•Oscillating foil in waves shows the possibility of 20% thrust increase even with small amplitude waves.