0. 



0.2 0.4 0.6 I 2 4 6 10 20 40 



PERIOD OF FREE OSCILLATION, W (s) 



100 



Figure 7. Measured and predicted natural periods of free oscillation of small 

 boat under various mooring arrangements (after Raichlen, 1968). 



breakwater, (c) motions of the breakwater, and (d) forces on the mooring 

 lines. The two-dimensional model was developed for the breakwater that is 

 assumed to be very long in one direction with the long-crested waves approach- 

 ing so that their crests are parallel to the long axis of the breakwater. 

 Under wind-wave conditions, this situation is rarely achieved; however, 

 studies of boat waves near floating breakwaters (Stramandi, 1975) indicate 

 that such waves often approach parallel to the long axis of the breakwater. 

 As a design tool, this two-dimensional theoretical model by Adee, Richey, and 

 Christensen (1976) will conservatively estimate wave transmission coefficients 

 and mooring forces. Solutions of the hydrodynamic equations formulated in 

 terms of the boundary value problem are difficult because of the nonlinearity 

 of the free-surface boundary condition; however, an approximate solution may 

 be obtained if this condition is linearized. This restriction theoretically 

 limits the applicability to cases of small incident wave amplitude and small 

 motion response of the breakwater. 



38 



