1. Offset Floating Breakwater Configuration . 



A fixed, rigid wall normal to the direction of wave travel will reflect 

 the incoming wave train and produce standing waves in front of the wall (the 

 amount of the reflection depends on the penetration of the wall beneath the 

 water surface). Large forces are required to hold a floating structure in a 

 fixed position, and it is not possible to anchor such a structure to prevent 

 all movement (resulting in wave regeneration). An offset breakwater config- 

 uration has been developed and patented (Sethness and Moore, 1973; Dailey, 

 Moore, and Sethness, 1974; Sethness, Moore, and Sabathier, 1974; Sethness, 

 Moore, and Dailey, 1975) (Fig. 189), which reduces the external forces 

 required to restrict the motion of the structure by making half of the wave 

 work against the other half. When the crest of one wave is pushing against 

 one set of offset surfaces, the trough of the wave is at the other set of 

 surfaces, producing an opposing force. The ratio of the force on the offset 

 configuration, F of f set , to that on a vertical rigid wall, F rigi( i wa ll» is 

 presented in Figure 190. Here, a is the wave amplitude, and h the 

 penetration of the structure below the Stillwater level. 



INCIDENT WAVES 



T 



D = L/2 

 o 



o plan view D = one-half 



design wavelength 



CB) ELEVATION VIEW 



Figure 189. Offset floating breakwater configuration, 

 showing pressure distribution on reflecting 

 surfaces (after Sethness and Moore, 1973). 



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