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In this paper a comparison between model basin experiments and results of diffraction computations on side-by-side moored LNG carriers is presented. The computations are based on a new lid method in diffraction codes to suppress non-realistic high wave elevations between the two floating objects. This lid method was originally formulated by Chen (2005). In this method a damping value is added to the free surface by means of a damping parameter. Since no theoretical solution can be found to establish the required value of the damping parameter, model basin experiments have been performed to determine this value. However from the results of the model basin experiments it is shown that it is difficult to obtain one unique value of the lid damping (for the 4m or small gap). The way of tuning the damping value of the lid is crucial. Tuning the damping based on first order results, like motions or wave height RAO’s will lead to a much larger variation in the estimate of the second order sway wave drift force transfer function.

This paper reports on extensive experiments on nonlinear wave groups that evolve in a hydrodynamic laboratory over long distances (200 m) from the generation of simple bichromatic waves. The deepwater experiments show large deformations of the wave group, with large increase of wave heights, depending on the value for the quotient of wave amplitude and frequency difference. The experimental results show little dissipation and reflections are virtually absent. A very efficient and accurate numerical code based on the full nonlinear surface wave equations, which has been developed for this purpose, reconstructs the experiments and enables one to investigate the evolution over much longer distances (reported here until 1,200 m) than in the laboratory.

The presented research is part of the development of an onboard wave and motion estimation system that aims to predict wave elevation and vessel motions some 60–120 s ahead, using wave elevation measurements by means of X-band radar. In order to validate the prediction model, scale experiments have been carried out in short crested waves for 3 different sea states with varying directional spreading, during which wave elevation and vessel motions were measured. To compare predicted and measured wave elevation, three wave probes were used at different distances from a large set of wave probes that was used as input to the model. At one of the prediction locations, also tests were performed to measure vessel motions. This setup allowed validation of a method that was used for initializing the linear wave prediction and ship motion prediction model. Various observations and conclusions are presented concerning optimal combinations of prediction model parameters, probe set-up and sea state.

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This paper reports on a feasibility study of potential floating structures suitable for wind turbines in shallow seas (around 50 m). It describes the concepts, the evaluation and the selection process and includes ancillary issues, such as grid connection and O & M. Finally, it reports detailed analysis of the concept selected as most suitable in the circumstances, namely, a ‘triple-floater’ construction. A main conclusion is that although, in this case, this technology may not yet be ready for commercial application, the gap to economic viability is closing.

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