In this paper, we propose the modified mild-slope equation that is able to treat with waves scattering against a vertical barrier, ignoring the local effects. This equation includes a scattering term in terms of the reflection coefficient of a single barrier. As well as the numerical results, we present two theoretical solutions to demonstrate the performance of the proposed mild-slope equation for two scattering problems; the first one is for the scattering problem due to widely spaced multiple barriers, and the second one is for the resonant problem due to a single barrier constructed at a rectangular harbor. Good agreement between theoretical and numerical solutions is found in both problems.
The breakwater of surface-piercing type has been developed mainly for application within bays or estuaries that are semi-protected from the direct impact of large waves. Most of bays have soft foundation which is too weak to bear the weight of gravity type breakwater. Thus the surface-piercing breakwater is taken into account as an alternative tool to reduce wave heights in the bay to an acceptable level. Differently from the ordinary breakwater of gravity type, the surface breakwater reduces the transmitted waves mainly due to the reflection of incident waves from the barrier body. Traditional breakwaters, seawalls and jetties reflect or direct wave energy in destructive ways or concentrate it in local hot spots so that the concentrated energy leads to the destruction of marine facilities. Among a number of breakwaters, the vertical barriers with gaps are recently favored from the point of view of marine environment since they do not in general partition the natural sea. Free exchange of water mass through the structures is possible so that the water in the sheltered region can be kept circulating and therefore prevent stagnation and pollution.
