Comprehensive Verification and Validation of a CFD Analysis

Abstract

Abstract Wave energy converters (WECs) are designed to operate near the resonance region, being excited at or close to its natural frequencies. Therefore, they are strongly affected by the interaction with waves, motion and mooring restraints. Floating WECs, such as point absorbers, present small dimensions in relation to the wave length, being typically subjected to large amplitude motions. An oscillating floating vertical cylinder is a simple representative geometry of WECs and component of many different floating structures. Over the past years it has been addressed in multiple studies revealing several difficulties. The pitch and heave free decay responses of a floating vertical cylinder will be studied throughout this paper. The present case was based on an experiment and subject of different CFD validation studies. Both have found significant discrepancies regarding the damping and natural period of the system, specially for the pitch motion. Throughout this work a rigorous verification study was performed, with special focus on the iterative convergence and discretisation errors relative to the hydrodynamic damping coefficients. Moreover, the main phenomena contributing to the hydrodynamic damping of the system were identified. Furthermore, the results were further compared with an experimental investigation.