Prediction of Occurrence of Breaking Waves in Deep Water

Abstract

A method to evaluate the frequency of occurrence of breaking waves in deep water is developed based on the joint probability distribution of wave excursion and associated time interval for a non-narrow-band random process. Wave breaking that takes place along an excursion crossing the zero-line as well as that which occurs along an excursion above the zero-line is considered. The breaking criterion is obtained from measurements of irregular waves generated in the tank. It is found that the functional relationship between wave height and period at the time of breaking of the irregular waves is by and large different from that known for regular waves. Comparisons between computed and observed frequencies of occurrence of wave breaking made for four different sea conditions generated in the tank show reasonably good agreement. The effect of sea severity on the frequency of occurrence of breaking waves is obtained by carrying out numerical computations using a family of wave spectra. The probability of occurrence of breaking waves depends to a great extent on the shape of the wave spectrum. The probability increase significantly with increase in the fourth moment of the spectrum irrespective of sea severity.