Three-dimensional computational fluid dynamics simulation of the impact of a rogue wave on a semi-submersible platform is undertaken using the Smoothed Particle Hydrodynamics (SPH) technique. Waves impacting the platform at a range of different angles are investigated for two different mooring systems: a Tension Leg Platform (TLP) system and a Taut Spread Mooring (TSM) system. The heave and surge responses of the platform are significantly different for the two mooring systems. The TSM system undergoes large heave but comparatively smaller surge motion than the TLP system. The degree of pitch is also very similar. The effect of wave impact angle is surprisingly small except for it's affect on the peak cable tension. The total tension in the leading mooring cable increases by approximately 1.6 times as the wave impact angle increases from 0º to 45º, having significant implication for mooring integrity. SPH is seen to be an attractive alternative to standard methods for simulating the coupled interaction of highly non-linear breaking waves and structural motion.
When small amplitude waves interact with geometrically simple structures, good prediction of the coupling between the waves and structure can be made using mathematical approaches that approximate the interaction and dynamics, (see e.g. Faltinsen 1990, Jain 1997). As the structures become more complex, the prediction becomes more difficult and numerical analysis using techniques such as boundary integral methods becomes necessary to account for the effect of waves (e.g. Nielsen 2003). However, irregular and larger amplitude waves can be highly non-linear and good prediction becomes increasingly difficult. Wave-structure interaction in such cases involves many interacting phenomena including flow separation, highly deformed wave interfaces, reflections and refractions, air entrainment and structural deformation. Typically, wave tank testing is used to predict this type of interaction, however this can be time consuming and expensive. It is desirable to have analytic and/or computational tools to perform analyses in the early stages of design to reduce the number of different design alternatives that require wave tank testing.
