The wave attenuation properties of a long floating pontoon breakwater of rectangular section with a vertical wave wall on the front face are investigated theoretically. The structure is partially restrained by vertical piles and can respond only in heave to wave excitation. The fluid motion is idealized as two-dimensional linearized potential flow and the solution for the fluid motion is obtained by the boundary integral equation method using an appropriate Green's function. Numerical results are presented to illustrate the effects of the various wave and structural parameters on the efficiency of the breakwater as a barrier to wave action. It is found that the wave reflection properties of the structure depend strongly on the draft of the wave wall and that by varying the wall draft and the pontoon draft and width, acceptable wave attenuation can be achieved over a range of wave conditions. The practical efficiency of this kind of wave barrier is then demonstrated by considering a typical protoype pontoon wave wall system and studying its behavior in a random wave environment.
Floating breakwaters offer an alternative to conventional fixed breakwaters and may be preferred in relatively low wave energy environments or where water depth or foundation considerations preclude the use of a bottom-founded structure. Furthermore, in certain applications, aesthetic or water circulation considerations may require that the breakwater does not pierce the free-surface and/or extend down to the sea-bed. In the present paper, the behavior of a long floating pontoon breakwater of rectangular section with a vertical wave wall on the front face is studied. Various aspects of the two-dimensional problem of wave interaction with long submerged, bottom-founded or floating, surface-piercing structures of rectangular cross-section have been studied previously by several investigators.
