Hydrodynamic simulation of a floating wave energy converter by a U-tube rig for power take-off testing

• Published in: Ocean engineering Vol. 37; no. 14; pp. 1253 - 1260
• Main Authors: Falcão, A.F. de O., Pereira, P.E.R., Henriques, J.C.C., Gato, L.M.C.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.10.2010; Elsevier
• Subjects: Applied fluid mechanics; Applied sciences; Buildings. Public works; Converters; Direct power generation; Electric generators; Electric power generation; Energy; Energy of waters: ocean thermal energy, wave and tidal energy, etc; Exact sciences and technology; Fluid dynamics; Fluid flow; Fundamental areas of phenomenology (including applications); Hydraulic constructions; Hydrodynamics; Hydrodynamics, hydraulics, hydrostatics; Marine; Model testing; Natural energy; Offshore structure (platforms, tanks, etc.); Oscillating; Oscillating body; Physics; Power take-off; Simulation; U-tube; Wave energy; U-tube; Wave energy; Oscillating body; Model testing; Power take-off; Wave effect; Energy convertor; Hydrodynamics; U shaped pipe; Hydraulic power; Energy of waters; Example; Numerical simulation; Model test; Simulation model; Offshore structure; Floating body
• DOI: 10.1016/j.oceaneng.2010.05.007
• ISSN: 0029-8018

Floating oscillating-bodies constitute an important class of offshore wave energy converters. The testing of their power take-off equipment (PTO) (high-pressure hydraulics, linear electrical generator or other) under realistically simulated sea conditions is usually regarded as a major task. A laboratory rig, consisting of a U-tube enclosing an oscillating column of water driven by a time-varying air-pressure, was devised to simulate the hydrodynamics of an oscillating buoy absorbing energy from sea waves, especially the inertia and the resonant frequency of the oscillating body. The PTO force is applied (by means of a piston) on one of the ends of the U-tube oscillating water column, whereas the other end is subject to a controlled time-varying air pressure. This is found to provide a reasonably realistic way of testing the PTO system (including its control) at an adequate scale (say about 1:5 to 1:4), which would avoid the use of a much more expensive experimental facility (very large wave tank) or testing in real wind-generated sea-waves. The matching conditions that the U-tube geometry and the driving time-varying air pressure must meet to ensure an adequate simulation are derived. These conditions leave some freedom to the U-tube rig designer and operator, allowing practical and engineering issues to be taken into account.