For the example problem, when 

 z = , 



AX(0) 



>= ^ (t)" 



cosh (47rd/L) C 

 sinh2(27rd/L) ' 1. 



(ttH)^ cosh(47Td/L)_ (;r4)^ (1.899) 



2L sinh^(27rd/L) 2(200) (0.6705)' 



= 1.67 ft. 



(d) The first-order approximation for pressure under a wave is; 



pgH cosh [27r(z + d)/L] 



P = 



cosh (27rd/L) 



cos 6 — pgz . 



when 



and when 



6 = (i.e. the wave crest), cos = 1, 

 27r(z + d) 



z = — d, cosh 



= cosh(O) =1.0 



Therefore 



(2) (32.2) (4) 1 

 p = — — - (2) (32.2) (- 20) = 107 + 1288 = 1395 lbs/ ft^ 



M J. (^U^ 



at a depth of 20 feet below the SWL. The second-order terms 

 according to Equation 2-56 are 



3 -nW tanh(27rd/L) 



8 ^^ IT sinh' (27rd/L) 



1 ttH^ tanh (27rd/L) 



cosh [47r(z + d)/L] 1 

 sinh' (27rd/L) 3 



cos 26 



sinh' (27rd/L) 



cosh 



47r(z + d) 



Substituting in the equation: 



3 ,o^ .oo .. '^(4)' (0.5569) 



- (2) (32.2) 



8 200 (0.6705)' 



1 



(0.6705)' 



(1) 



-i (2) (32.2) ^_(i)- (0-5569) , , 

 8 200 (0.6705)' 



2-46 



