Given the orientation of a pile in the flow field, the total wave 

 force acting on the pile can be expressed as a function of these variables. 

 The variation of force with distance along the pile depends on the mecha- 

 nism by which the forces arise, that is, how the water particle velocities 

 and accelerations cause the forces. The following analysis relates the 

 local force, acting on a section of pile element of length dz to the 

 local fluid velocity and acceleration that would exist at the center of 

 the pile, if the pile were not present. Two dimensionless force coeffi- 

 cients, an inertia or mass coefficient Cyi^ and a drag coefficient Cp, 

 are used to establish the wave-force relationships. These coefficients 

 are determined by experimental measurements of force, velocity, and 

 acceleration or by measurements of force and water surface profiles with 

 accelerations and velocities inferred by assuming an appropriate wave 

 theory. 



The following discussion initially assumes that the force coefficients 

 Cm and C[) are known, and illustrates the calculation of forces on verti- 

 cal cylindrical piles subjected to monochromatic waves. A discussion of 

 the selection of Cm and Cd follows in Section 7.315, Selection of 

 Hydrodynamic Force Coefficients, C^ and C^. Experimental data are avail- 

 able primarily for the interaction of nonbreaking waves and vertical cylin- 

 drical piles. Only general guidelines are given for the calculation of 

 forces on noncircular piles. 



"^77777777777777777777777777777777777777777777777777777777777777777 



Figure 7-39. Definition Sketch of Wave Forces on a Vertical Cylinder 



7-65 



