and it is desired to calculate the wave height and direction in a water depth of 40 feet. From 

 the observed information 



Lo = 737.3 



H/Lo = 0.0271 



h/Lo = 0.0814 (h = 60 ft) 



h/Lo = 0.0542 (h = 40 ft) 



Examining the available figures, it is seen that the deepwater wave direction is between 

 10° and 20°. As a close approximation, the problem is solved for a^ = 10° and a^ = 20°, 

 and the desired results obtained by interpolation. For a^ = 10°, from Figure 26, a line 

 passing through H/Lp= 0.0271, h/L^ = 0.0814 is sketched with the same approximate 

 shape as those for H^/L^ - 0.02 and 0.04 to determine H/L^ = 0.033 and a = 6.2° for 

 hl\ = 0.0542. The corresponding values for a^ = 20° are H/L^ = 0.031 and a = 12°. The 

 procedure is shown graphically in Figure 39 for a^ = 10°. Because for a^ - 10° and 20°, the 

 a values corresponding to h/L^ = 0.0814 and H/L^ = 0.0271 are 6.8° and 13° respectively, 

 and the desired a for these conditions is 11°, the values of H/L^ and a for h = 40 feet may 

 be determined by linear interpolation as: 



^ = 0.033 + ['III Z g°Qaj (11° - 6.8°) = 0.032 



or 



and 



H = (737.3) (0.032) = 23.6 ft 



a = 6.2° + J13I I l[ll] (11° - 6.8°) = 10.1° 



Dissipative mechanisms such as percolation and bottom friction are not included in these 

 results, and in many cases these mechanisms will be of greater significance than the 

 nonlinear effects on the celerity and group velocity which represent the difference between 

 the results presented here and the Unear wave theory. 



Example 7— Use of Tables for Nontabulated Wave Conditions 



Most of the previous examples have been presented for wave conditions which were 

 available as one of the 40 tabulated cases, i.e., Case 4-D. It is anticipated that the tabulations 

 will be used primarily for preliminary design, and therefore that the 40 cases may provide 

 adequate information for this purpose without interpolation. Final design of, for example, a 



86 



