An experimental study on deterministic freak waves: Generation, propagation and local energy

• The application scope of a phase–amplitude iteration for freak waves is identified.
• Reasonable estimates of freak wave speeds are obtained with trough-to-trough periods.
• The quadratic phase coupling phenomenon between freak wave components is revealed.

An experimental investigation on deterministic freak waves is presented here. Four similar freak wave sequences with different wave steepness values were used as the target waves in the experiments. A phase–amplitude iteration method was adopted to generate these deterministic freak wave sequences in the wave flume. The results demonstrate that the phase iteration considerably improves the modeling in the first optimization and becomes less effective for subsequent optimizations. The method is more likely to achieve well-matching results for small steepness target waves through phase iterations. Wave speeds and wave energy distributions of analyzed freak waves were also investigated. Reasonable estimates of wave speeds were achieved by adopting trough-to-trough periods and wave heights of freak waves according to third-order Stokes wave theory. The quadratic phase couplings between the first-harmonic component and higher-harmonic components were significant.