Effects of machine nonlinearity on the performance of idealised wave-energy converters

• Main Authors: Manasseh, Richard, Hasan, Md. Kamrul, Leontini, Justin S., Puticiu, Liviu, De Chowdhury, Swapnadip
• Other Authors: Swinburne University of Technology
• Format: Conference Object
• Language: unknown
• Published: 2017
• Subjects: Southern Ocean
• Online Access: http://hdl.handle.net/1959.3/438035; http://www.ewtec.org/ewtec-2017/

Calculations are presented on the nonlinear behaviour of generic wave energy converters. Two classes of nonlinearity are considered: the nonlinearity due to the inertia of the machine, and the nonlinearity due to fluid-dynamical dissipation. The inertial nonlinearity represents the machine’s buoyancy, or the mass of water within it, varying during the machine’s stroke. Of all the nonlinear phenomena, the modelling of the dissipation is found to be most problematic. Dissipative nonlinearities comprise turbulent boundary-layer dissipation and vortex formation around the machine. These are empirically modelled as terms in the ordinary differential driven-oscillator equations of motion of the machine, determined by a scan through parameter space using Direct Numerical Simulations. For conditions typical of the Southern Ocean, it is found that nonlinearity could adversely affect performance and that the nonlinearity due to vortex formation causes the most serious reduction in response amplitude.