This study develops further the conceptual model of Oscillating Wave Surge Converter (OWSC) hydrodynamics and improves the representation of hydrodynamic torques in the device's nonlinear time domain numerical model. Wave excitation torque tests were used to evaluate how the wave excitation torque experienced by a static OWSC varies with wave period and amplitude for a range of OWSC pitch angles. Forced oscillation tests were used to evaluate how the radiation torque experienced by an OWSC, due to its motion through still water, varies with oscillation period, oscillation amplitude and angular velocity. A third set of experiments, in which the restoring moment of buoyancy was augmented with mechanical springs, referred to as buoyancy simulation tests, demonstrated how modifications to the static torque of the system influences OWSC motion, The experiments validated and identified the limits of linear hydrodynamic coefficients obtained using Boundary Element Method (BEM) codes. Numerical methods were evaluated on their ability to improve the representation of the measured torques not estimated by the BEM codes. The wave excitation and buoyancy simulation tests were performed in 4.5m and 16m wide wave tanks at Queen's University Belfast (QUB). This presented the unique opportunity to observe how wave tank characteristics can influence experimental measurements. The buoyancy simulation tests also calibrated and validated an enhanced nonlinear time domain numerical model. The enhanced nonlinear time domain numerical model contained the numerical methods that were found to improve the estimates of the wave excitation and radiation torques measured during the wave excitation torque and buoyancy simulation tests. The enhanced nonlinear time domain numerical model contained a pitch angle dependent wave excitation torque, a nonlinear state-space approach to modelling radiation torque, an empirically developed drag torque term and an analytically derived nonlinear hydrostatic torque.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:725744 |
| Date | January 2017 |
| Creators | Crooks, David Joel |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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