The original aim of the research project was to investigate the mechanism of power capture from sea waves and to optimise the performance of a vee-shaped floating Wave Energy Converter, the Floating Clam, patented by Francis Farley. His patent was based on the use of a pressurised bag (or ‘reservoir’) to hold the hinged Clam sides apart, so that, as they moved under the action of sea waves, air would be pumped into and out of a further air reservoir via a turbine/generator set, in order to extract power from the system. Such “Clam Action” would result in the lengthening of the resonant period in heave. The flexibility of the air bag supporting the Clam sides was an important design parameter. This was expected to lead to a reduction in the mass (and hence cost) of the Clam as compared with a rigid body. However, the present research has led to the conclusion that the Clam is most effective when constrained in heave and an alternative power take-off is proposed. The theoretical investigations made use of WAMIT, an industry-standard software tool that provides an analysis based on potential flow theory where fluid viscosity is ignored. The WAMIT option of Generalised Modes has been used to model the Clam action. The hydrodynamic coefficients, calculated by WAMIT, have been curve-fitted so that the correct values are available for any chosen wave period. Two bespoke mathematical models have been developed in this work: a frequency domain model, that uses the hydrodynamic coefficients calculated by WAMIT, and a time domain model, linked to the frequency domain model in such a way as to automatically use the same hydrodynamic and hydrostatic data. In addition to modelling regular waves, the time domain model contains an approximate, but most effective method to simulate the behaviour of the Clam in irregular waves, which could be of use in future control system studies. A comprehensive series of wave tank trials has been completed, and vital to their success has been the modification of the wave tank model to achieve very low values of power take-off stiffness through the use of constant force springs, with negligible mechanical friction in the hinge mechanism. Furthermore, the wave tank model has demonstrated its robustness and thus its suitability for use in further test programmes. The thesis concludes with design suggestions for a full-scale device that employs a pulley/counterbalance arrangement to provide a direct connection to turbine/generator sets, giving an efficient drive with low stiffness and inherently very low friction losses. At the current stage of research, the mean annual power capture is estimated as 157.5 kW, wave to wire in a far from energetic 18 kw/m mean annual wave climate, but with scope for improvement, including through control system development.

[Truncated abstract] The fracture of brittle materials in uniaxial compression is a complex process with the development of cracks generated from initial defects. The fracture mechanism and pattern of crack growth can be altered considerably by the presence of a free surface. In proximity of a free surface, initially stable cracks that require an increase in the load to maintain the crack growth can become unstable such that the crack growth maintains itself without requiring further increase in the load. This leads to a sudden relief of accumulated energy and, in some cases, to catastrophic failures. In the cases of rock and rock mass fracturing, this mechanism manifests itself as skin rockbursts and borehole breakouts or as various non-catastrophic forms of failure, e.g. spalling. Hence, the study of crack-boundary interaction is important in further understanding of such failures especially for the purpose of applications to resource engineering. Two major factors control the effect of the free boundary: the distance from the crack and the boundary shape. Both these factors as well as the effect of the initial defect and the material structure are investigated in this thesis. Three types of boundary shapes - rectilinear, convex and concave - are considered. Two types of initial defects - a circular pore and inclined shear cracks are investigated in homogeneous casting resin, microheterogeneous cement mixes and specially fabricated granulate material. The preexisting defects are artificially introduced in the physical model by the method of inclusion and are found to successfully replicate the feature of pre-existing defects in terms of load-deformation response to the applied external load. It is observed that the possibility of crack growth and the onset of unstable crack growth are affected by the type of initial defect, inclination of the initial crack, the boundary shape and the location of the initial defect with respect to the boundary. The initial defects are located at either the centre or edge of the sample. The stresses required for the wing crack initiation and the onset of unstable crack growth is highest for the initial cracks inclined at 35° to the compression axis, lowest at 45° and subsequently increases towards 60° for all the boundary shapes and crack locations. In the case of convex boundary, the stress of wing crack initiation and the stress of unstable crack growth are lower than for the case of rectilinear and concave boundary for all the crack inclinations and crack locations. The crack growth from a pre-existing crack in a sample with concave boundary is stable, requiring stress increase for each increment of crack growth. The stress of unstable crack growth for the crack situated at the edge of the boundary is lower than the crack located at the centre of the sample for all the crack inclinations and boundary shapes.