Table 2. Computer program output for example problem 2. 



***» IRREGULAR WAVES **•* 



N L(FT) B(FT) HU(fT) H(PT) T(StC) OS(FT) HS(FT) TANT Q* ALPHA 



fl «00.00 125.00 7.8 8,o 7.0 12,0 13.0. .hb7 .Ol'O ,053o 



CD COE ACMFT?) RU*UP(fT) QOCCFS} PCFT) K V(FPS) 



.8 1.0 1000.00 7,17 5.<»i 2.2«8 7,12 1.33 



*************** EXAMPLE PROBLEM 3*************** 



GIVEN : Three rubble-mound offshore breakwaters are located with d s = 12 feet 

 (3.7 meters), I = 250 feet (76.2 meters), tan 9 = 0.667, and A ce = 1,440 

 square feet (134 square meters) . 



FIND : The influence of breakwater freeboard, incident wave height, wave period, 

 gap spacing, and shore attachment on V. 



SOLUTION : The computer program was used to make these calculations and results 

 are given in Figures 7 to 10. Figure 7 shows that an increase in breakwater 

 freeboard or gap to length ratio causes V to decrease. An increase in in- 

 cident wave height and in wave period produces an increase in V as expected 

 (Figs. 8 and 9). Shore attachment with impermeable walls forces more flow 

 through breakwater gaps than for a detached system (Fig. 10). The most dra- 

 matic effect of s hor e attachment occurs for relatively_small breakwater gaps. 



*************************************** 



IV. SUMMARY AND CONCLUSIONS 



A method is presented for estimating the first approximation of the water 

 velocity and flow rate through breakwater gaps caused by wave overtopping. 

 Calculations can be performed either by hand, using a dimensionless curve, or 

 by a computer program, BWFL0W2, available in the Corps of Engineers Computer 

 Library. Examples of both calculation methods are given to illustrate the 

 relative influence of various design parameters on the magnitude of the gap 

 velocity, V. It is suggested that V not exceed 0.5 foot per second. High 

 values of T may produce scour around structures and transport sediment out 

 of the zone protected by the breakwaters. 



