Developments of a generalized new wave theory to advance coastal hydrodynamics

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Toward the establishment of a general theory on water waves, numerical analysis and laboratory experiments on wave breaking were executed first in this study. Their results revealed that when a wave breaks the vertical pressure gradient becomes zero near the wave crest, suggesting that the vertical pressure gradient may be used as a useful breaking criterion. Incorporating this criterion into the wave model by Nadaoka et al. (1994-97), which can describe wave evolution at arbitrary depths under nonlinear and dispersive effects, a numerical simulation was performed for wave train traveling over a slope. The numerical results on the breaker depth show good agreements with those by Goda's empirical criterion. A breaking wave model was also developed in which a depth-integrated formulation is employed and the turbulence energy source due to the large-eddy production at the breaking wave crest is formulated. This model was demonstrated to give satisfactory results even for irregular waves breaking over slopes with various profiles. As another main subject of the study, phase-averaged models both for the Boussinesq equations and Nadaoka et al's equations were developed. These phase-averaged type models may serve CPU time quite efficiently and simulate nonlinear evolution of carrier and associated long waves. In relation to this work, a field observation was performed at Kajima port facing the Pacific Ocean to reveal the characteristics of long waves associated with group waves. Further the wave model by Nadaoka et al.was extended to handle waves generated by impinging of water mass overtopping a breakwater.