a b s t r a c tThe performance of a new type of flow energy harvester based on oscillating foils is investigated through numerical modeling by using two methods, a 2D thin-plate model and a 3D nonlinear boundary-element model. The fluid-structure interaction problem involved in the dynamics of a heaving/pitching foil coupled with an actuation/energy harvesting system in this device is examined. The 2D analysis allows us to simulate dynamics of the flapping-foil system over a large range of parameters and to identify areas of special interests (e.g., high energy output or high efficiency). In the vicinity of these areas the 3D model can accurately predict the performance of the system. By examining the power extraction capacity and efficiency of the system at various geometric, mechanical, and kinematic parameters, the optimal performance of the system is determined. In addition, the performance is found to be enhanced by the presence of a solid ground, as well as the thickness of the foil (at certain frequencies).

A novel CFD-based approach is presented that is used in conjunction with model test experiments to predict ship resistance at full-scale Reynolds and Froude numbers. It relies on verification using model scale experiments, including an agreement of integrated shear force with established model-ship correlation lines at model and full-scale, and includes surface roughness effects. One major advantage of the method is that the geometric dimensions of the CFD modelling remain at model scale. CFD simulation results were successfully verified considering the drag of two different catamarans at 1:22 and 1:50 model scale. Furthermore, it is shown that an identical near-wall mesh can be used for both model and full-scale simulations without compromising the accuracy of the shear force. At full-scale the deviation of resistance between CFD prediction, model test extrapolation and full-scale measurements of a 98 m catamaran was as low as 5% at F r = 0.40 and 0.43. For a novel 130 m catamaran variations in full-scale drag for a smooth hull were also less than 5% when comparing extrapolated model scale experiments and CFD predictions. However, at such large Reynolds numbers CFD predictions for correlation and roughness allowance were significantly higher compared to estimates proposed in ITTC guidelines.

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