equation (7-68) for the horizontal velocity, and taking C^; 

 per unit length of pile near the breaker crest becomes 



'Dm'' ''d ^''''Irest ='0.88 pg DH^, 



= 1.75 , the force 



(7-69) 



Table 7-7 is a comparison between the result calculated from equation (7-69) 

 with measurements by Ross (1959) on a 1-f oot-diameter pile (Rg « 1.3 x 10 ) . 



Table 7-7. Comparison of measured and calculated breaker force. 



Values given are force per unit length of pile near breaker crest. 

 Calculated from equation (7-69). 

 Measured by Ross, 1959. 



Based on this comparison, the choice of C^j = 1.75 for Rg > 5 x 10 

 appears justified for calculating forces and moments due to breaking waves in 

 shallow water. 



(a) Calculation of Forces on Noncircular Piles . The basic force 

 equation (eq. 7-20) can be generalized for piles of other than those with a 

 circular cross section, if the following substitutions are made: 



irD 



= volume per unit length of pile 



(7-70) 



where 



D = width perpendicular to flow direction per unit length of pile 



7-159 



