Survivability of wave energy converters using CFD. (August 2017) - Ransley, E.J.
Abstract: The survivability of Wave Energy Converters (WECs) in extreme waves is a critical issue faced by developers; typically assessed via small scale physical experiments with considerable uncertainties. Until recently, confidence in the ability of numerical tools to reproduce extreme wave events and their interaction with floating structures has been insufficient to warrant their use in routine design processes. In this work a fully nonlinear, coupled tool for simulating focused wave impacts on generic WEC hull forms is described and compared with physical measurements. Two separate design waves, based on the 100 year wave at Wave Hub and using the NewWave formulation, have been reproduced numerically as have experiments in which a fixed truncated circular cylinder and a floating hemispherical-bottomed buoy are subject to these focused wave events. The numerical model is shown to reproduce the wave events well with some inaccuracies observed in shallower water depths. The results for pressure and run-up on the cylinder surface, as well as the high-order free-surface behaviour, also compare well with experimental results. The floating buoy's motion and mooring load are reproduced exceptionally well showing that the tool presented here can be used to assess WEC survivability and complement existing physical modelling. Highlights: A fully nonlinear numerical model, for assessing WEC survivability in extreme waves, using open-source CFD code, OpenFOAM ® . NewWave (based on 100 year wave at Wave Hub) interactions with both a fixed truncated cylinder and a moored floating buoy. Predictions of run-up and pressure (cylinder); motion and mooring load (buoy) compared with physical measurements. Successful prediction of complex hydrodynamics, large amplitude motions and mooring loads in design wave conditions.