From Figure 7-58, C^ = 0.7, which is the value used in the preced- 

 ing example. 



For the example with H = 50 ft., T = 10 sec, d = 100 ft., and 

 D = 1 ft., from Equation 7-40, 



max 



— 3.5 It. /sec. 



(10) (0.9) 



From Equation 7-39, 



(3.5) (1) 



From Figure 7-58, C^ = 0.9 which is less than the value of Cp = 1.2 

 used in the force calculation. Consequently, the force calculation 

 gave a high force estimate. 



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



b. Factors Influencing Cy^^. MacCamy and Fuchs (1954) found by theory 

 that for small ratios of pile diameter to wavelength. 



Cm = 2.0 . (7-45) 



This is identical to the result obtained for a cylinder in accelerated 

 flow of an ideal or nonviscous fluid. (Lamb, 1932.) The theoretical 

 prediction of C^ can only be considered an estimate of this coefficient. 

 The effect of a real viscous fluid, which accounted for the term involving 

 Cjj in Equation 7-41, will drastically alter the flow pattern aroimd the 

 cylinder, and invalidate the analysis leading to C/i^ = 2.0. The factors 

 influencing C^^ also influence the value of C^^. 



No quantitative dependence of Cm on Reynolds number has been 

 established, although Bretschneider (1957) indicated a decrease in 

 Cm with increasing Rq. However for the range of Reynolds numbers 

 (Rg < 3 X 10*^) covered by Keulegan and Carpenter (1956) , the value of 

 the parameter A/D plays an important role in determining Cm. For 

 A/D < 1 they found C^ =»2.0. Since for small values of A/D the 

 flow pattern probably deviates only slightly from the pattern assumed 

 in the theoretical development, the result of Cm = 2.0 seems reasonable. 

 A similar result was obtained by Jen (1968) who found Cm w 2.0 from 

 experiments when A/D < 0.4. For larger A/D values that are closer 

 to actual design conditions, Keulegan and Carpenter found a minimum 

 Cm « 0.8, for A/D « 2.5, and found that Cm increased from 1.5 to 

 2.5 for 6 < A/D < 20. 



7-108 



