Numerical and laboratory investigation of breaking of steep two-dimensional waves in deep water

Abstract

The paper extends a pilot study into a detailed investigation of properties of breaking waves and processes responsible for breaking. Simulations of evolution of steep to very steep waves to the point of breaking are undertaken by means of the fully nonlinear Chalikov–Sheinin model. Particular attention is paid to evolution of nonlinear wave properties, such as steepness, skewness and asymmetry, in the physical, rather than Fourier space, and to their interplay leading to the onset of breaking. The role of superimposed wind is also investigated. The capacity of the wind to affect the breaking onset is minimal unless the wind forcing is very strong. Wind is, however, important as a source of energy for amplification of the wave steepness and ultimately altering the breaking statistics. A detailed laboratory study is subsequently described. The theoretical predictions are verified and quantified. In addition, some features of the nonlinear development not revealed by the model (i.e. reduction of the wave period which further promotes an increase in steepness prior to breaking) are investigated. Physical properties of the incipient breaker are measured and examined, as well as characteristics of waves both preceding and following the breaker. The experiments were performed both with and without a superimposed wind, the role of which is also investigated. Since these idealized two-dimensional results are ultimately intended for field applications, tentative comparisons with known field data are considered. Limitations which the modulational instability mechanism can encounter in real broadband three-dimensional environments are highlighted. Also, substantial examination of existing methods of breaking onset detection are discussed and inconsistencies of existing measurements of breaking rates are pointed out.

Spectral wave modelling of Typhoon Krosa

“…Babanin et al, 2010), which is what the record shown in Liu et al (2008) and Doong et al (2009) demonstrates. In a quasi-twodimensional wave train with the mean steepness of (3), a wave breaking should develop within approximately 20 wave periods, leading to the wave having individual wave steepness of (Babanin et al, 2007). This is exactly the steepness of the highest wave with H = 32.3 m (1) shown in the record of some 30 waves by Liu et al (2008) and Doong et al (2009).…”

“…If the modulational instability is active, such steep-in-the-mean waves should develop modulation with a relatively low number of waves in the group (e.g. Babanin et al, 2010), which is what the record shown in Liu et al (2008) and Doong et al (2009) demonstrates. In a quasi-twodimensional wave train with the mean steepness of (3), a wave breaking should develop within approximately 20 wave periods, leading to the wave having individual wave steepness of (Babanin et al, 2007).…”

Coupling of wave and circulation models in coastal–ocean predicting systems: a case study for the German Bight

“…Babanin et al (2010) showed that interaction of turbulence and bottom stress is also very important.…”

Breaking characteristics and geometric properties of spilling breakers over slopes

“…As it propagates over a plane slope, the wave starts to deform and the wave front moves forward, thus the shape of the wave profile is not symmetric anymore. Several studies have been carried out to investigate the geometric properties of breaking waves in deep water (Babanin et al, 2010;Bonmarin, 1989;Kjeldsen and Myrhaug, 1978;Lader, 2002). Although a considerable amount of literature has been reported on wave steepness and asymmetry factors of shallow water waves (Adeyemo, 1968;Ippen and Kulin, 1954;Iwagaki and Sakai, 1972;Miller and Zeigler, 1964), there have been limited studies on the geometrical asymmetry associated with breaking waves on slopes in shallow water.…”