III. MEASURED PEAK WATER PATTERNS 



The preceding photo sequences show complicated free-surface effects 

 in wave flow at surface-piercing piles. The principal data reported are 

 measured peak water (or crest height) at various pile orientations rela- 

 tive to wave direction, which were extracted from the test records of the 

 complex flows investigated. 



Appendix C includes data sets of the measured patterns of peak water 

 versus pile orientation for which the test records have satisfactory 

 internal consistency. Still, these sets have a detectable variability: 

 repeated tests result in a slightly different pattern, and, with channeled 

 piles, there can be a ragged variation in measurement with small changes' 

 in orientation angle. However, each pile is expected to have a character- 

 istic peak water pattern related to its cross' section. 



This section presents data to establish general trends and to facili- 

 tate comparison of the patterns obtained with various piles. 



1. Circular Piles . 



The photo sequences show that crest stagnation at a circular pile 

 can be similar to that at a channeled pile. This is established as a 

 quantitative result by comparing peak water at an H-pile to that at a 

 circular pile. 



Figure 19 shows measured runup versus wave generator eccentric for 

 waves' on the 3-inch circular pile (a = 0°) and on the 2x2 H-pile (B = 0°) 

 in 96-foot tank tests. For most wave conditions the measured runup is 

 slightly higher at the channeled pile than at the smooth pile, although 

 this is reversed for the waves with T = 3.10 seconds. In these long- 

 period waves, there is less decrease in fluid velocity with depth below 

 the free surface; this lessens the downward secondary flow expected at 

 the front of the pile (Petryk, 1969), and might account for the relatively 

 higher runup at the circular pile with long waves. The data in Figure 19 

 reinforce the conclusion in Section II that crest stagnation at the front 

 of a circular pile is similar to that at a channeled pile. 



Figure 20 superposes polar patterns of [W(a)/W] for the 3-inch 

 circular pile and of [W(g)/F| for the 3x3 H-pile, although the angular 

 variable is fundamentally different (Fig. 1). The four wave conditions 

 cover the range used in the 96-foot tank. In each case, the similarity 

 in the shape of the patterns is notable: there is a broad front maximum 

 region, a rear secondary maximum, and intermediate symmetrically located 

 minimums. The magnitudes of the front and rear maximums and of the 

 minimums are fairly similar for the two piles. However, the maximum 

 in W(3) can occur away from 6=0" and the pattern variation with orien- 

 tation angle is more regular for the circular pile. Figure 20 partially 

 contradicts the results in Figure 19, showing W(6 = 0°) is larger than 

 W(a = 0°) in each case. This disagreement may be due to confinement 

 effects with the 3x3 H-pile in the 96-foot tank (see Sec. IV, 1). 



38 



