Extreme Waves in laboratory Generated Irregular Wave Trains

Large waves in experimental model scale random wave trains are investigated. Statistical distributions of crest heights, troughs and peak-to-peak wave heights are compared to the Rayleigh model and to linear numerical wave data. Wave heights are seen to agree well with the Rayleigh distribution. The largest individual waves from the experiment show asymmetric behaviour with higher crests and more shallow troughs than predicted by the linear theory. This is seen both from Weibull distribution plots and from wave profiles of individual large waves in the time domain. Particle velocities in extreme waves, estimated by linear transformations of wave elevation measurements, are particularly asymmetric and peaked. Proper design rules for extreme waves should be further developed. More knowledge on full scale waves must form a central part of this development.