s acts on a vertical circular pile with a diameter D = 0.3 m (1 ft) in a 

 depth d = 4.5 m (14.8 ft) . Assume % = 2.0 and C^j = 0.7 . 



FIND: The maximum transverse (lift) force acting on the pile and the 

 approximate time variation of the transverse force assuming that Airy theory 

 adequately predicts the velocity field. Also estimate the maximum total 

 force. 



SOLUTION ; Calculate, 



H 3.0 



= 0.0031 



2 2 



gT (9.8) (10) 



4.5 



= 0.0046 



2 2 



gT (9.8) (10) 



and the average Keulegan-Carpenter number "^^t^v. T/D , using the maximum 

 horizontal velocity at the SWL and at the bottom to obtain ^max * 



Therefore, from equation (7-23) with z = -d , 



_ H gT 1 

 \ maxjhottom 2 L 



(u K .. = ^^V7#TT^ (0-90) = 2.0 m/s (6.6 ft/s) 

 ^moic/ bottom 2 (65.5) 



2 

 where L. is found from Figure 7-68 by entering with d/gT and reading 



2 

 L./L = 2tiL /gT = 0.42 . Also, 1/cosh [2ird/L] is the K value on 



Figure 7-68. Then, from equation (7-23) with z = , 



/u \ =^^ 

 \^ max) SWL 2 L. 



/ \ 3.0 (9. 8) (10) „ „ , /7 o f^/ ^ 



1 "^^1 oin = —T- cir^ — = 2.2 m/s (7.2 ft/s) 



\ max J SWL 2 65.5 



The average velocity is therefore, 



_ \ "max/bottom \^max) SWL 



u 



max 



2.0 + 2.2 4.2 „ , , /^ n £^ / N 

 u = 7^ = — ;r- = 2.1 m/s (6.9 ft/s) 



max 2 2 



7-135 



