An experimental and numerical study of the freak wave speed

The propagation speed is one of themost important characteristics for describing freakwaves. The research of freak wave speed is not only helpful for understanding the generationmechanismand evolution process of freak waves, but also applicable to the prediction. A stable and accuratemethod is proposed for the calculation of the freak wave speed, in which physicalmodel tests are carried out tomeasure themotion of the largest wave crest along the wave tank. The linear regression relationship between the spatial position of the largest wave crest and instantaneous moment is established to calculate the speed of totally 248 cases of experimental freak waves and 312 supplementary cases of numerical freak waves. Based on the calculate results, a semitheoretical and semiempirical formula is proposed by using a regression analysis method to predict the speed of the freak wave, and the nonlinear characteristic of the freak wave speed is also investigated.