Wave Refraction Analyses at the Coast of Norway for Offshore Applications

The wave load on potential offshore wind farms off Norway is studied by the use of a numerical wave refraction model. The model estimates trajectories of wave energy (rays) for waves propagating in water with varying surface velocity. The calculations indicate that for southerly and southwesterly winds the majority of shoreward propagating waves will converge in the coastal area off southwestern Norway. For offshore wave propagation directions equal to 180o and 210o, respectively 88% and 72% of the shoreward propagating rays approaches land south of Ålesund on the western part of Norway. For westerly and northerly winds the distributions are approximately uniform. It is further found that in the case of southerly or southwesterly winds, waves approach- ing the southern part of Norway are frequently misaligned with the wind. This will result in an increased bending moment of the masts. For offshore wave propagation direction between 180o and 240o the calculations indicate that approximately 24% of the rays reaching the coast of Norway along its southwestern part deviates by more than 45o of offshore propagation direction.