From Equation l-ll , 



^L = ^L^ DH^K^m ^°s20 = F^^ cos 20. 

 The maximum transverse force F]^^ occurs when cos 20 = 1.0. Therefore, 



(2) (32.2) 



Lm 



= 0.7 ^-^ (1)(10)2 (0.7) = 1,580 ]bs., 



where Kj^ is found as in the preceding examples. For the example 

 problem the maximum transverse force is equal to the drag force. 



Since the inertia component of force is small (preceding example), 

 an estimate of the maximum force can be obtained by vectorial ly adding 

 the drag and lift forces. Since the drag and lift forces are equal 

 and perpendicular to each other, the maximum force in this case is 

 simply. 



F. 



Lm 1580 



-^.,. o = 2,230 lbs.. 



'"'^ cos 45° 0.707 



which occurs about when the crest passes the pile. 



The time variation of lift force as given by, 



F^ = 1,580 cos 20, 

 is shown in Figure 7-57. 

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



7.315 Selection of Hydrodynamic Force Coefficients C^ and C^. Values 



of Cj^, Cjj and safety factors given in the sections that follow are 



suggested values only. Selection of Cm, Cd and safety factors for a 

 given design must be dictated by the wave theory used and the purpose of 



the structure. Values given here are intended for use with the design 

 curves and equations given in preceding sections for preliminary design 

 and for checking design calculations. More accurate calculations require 

 the use of appropriate wave tables such as those of Dean (1973) or 

 Skjelbria, et al. (1960) along with the appropriate Cm and Cd. 



a. Factors influencing Cj^, The variation of drag coefficient C^ 

 with Reynolds Number Rg for steady flow conditions is shown in Figure 

 7-58. The Reynolds Number is defined by, 



R = ^. (7-38) 



7-99 



