Wiegel and Delmonte 



Sarpkaya, 1963). A theory was developed which was used as a guide 

 in analyzing laboratory data taken of the uniform acceleration of a 

 circular cylinder in one direction. Figure 2 shows the relationship 

 they found between Cj) and Cj^ , which was dependent upon / /d, 

 where H is the distance travelled by the cylinder from its rest po- 

 sition and D is the cylinder diameter. They indicated "steady state" 

 (i. e. , for large value of X /D) values of Cq = 1.2 and Cj^ =1.3. 



The results shown in Figure 2 are different than those found 

 by McNown and Keulegan (1959) for the relationship between Cq and 

 Cm in oscillatory flow. They measured the horizontal force exerted 

 on a horizontal circular cylinder placed in a standing water wave, 

 with the cylinder being parallel to the bottom, far from both the free 

 surface and the bottom, and with the axis of the cylinder normal to 

 the direction of motion of the water particles. The axis of the cylin- 

 der was placed at the node of the standing wave so that the water par- 

 ticle motion was only horizontal (in the absence of the cylinder). 

 Their results are shown in Figure 3. Here, T is the wave period 

 and T is the period of a pair of eddies shedding in steady flow at 

 a velocity characteristic of the unsteady flow. The characteristic 

 velocity was taken as the maximum velocity. They found that if 

 T/T e was 0. 1 or less, separation and eddy formation were relati- 

 vely unimportant, with the inertial effects being approximately those 

 for the classical unseparated flow, and if T/T e was greater than 10, 

 the motion was quasi- steady. 



"LIFT" FORCES EXERTED ON A VERTICAL PILE BY PROGRES- 

 SIVE WATER WAVES 



Water Particle Motion and Eddies 



Studies in the Hydraulic Laboratory of the University of Cali- 

 fornia have been made by Bidde (1970, 1971) for the case of "deep 

 water" and "transitional water" waves acting on a vertical "rigid"* 



* The problems associated with a flexible pile are more compli- 

 cated, owing to interaction of the pile motion and the formation of 

 eddies. The reader is referred to the work of Price (1952) and Laird 

 (1962, 1965) for details. The problem of an array, with the fluid 

 flow - eddy interactions is also more complicated, and the reader is 

 referred to papers by Laird and his colleagues for details on this 

 subject (I960, 1963). 



766 



