Galvin and Hallermeier (1972) introduced the zero-crossing method 

 for determining the front symmetry £oint of^ a simple pattern. TMs uses 

 the zero crossing of the quantity [H(6) - H(B+180°)] or [W(6) - W(B+180°)] 

 to locate the angle separating the front from the back of the pattern; 

 this ang]_e is ,90° away from the front symmetry point. Figure D-3 shows 

 [H(i|^) - H(((j+180°)] for the two patterns in Figure D-2. Each pattern has 

 a well-defined symmetry point located in the direction between the two 

 generators . 



Of the nine tests discussed here, five were run with either one or 

 the other generator operating, and four were run with two wave trains. 

 Figure D-4 shows the ratio of the computed velocity heads' in the two 

 wave trains versus the measured zero-crossing angle of the resulting 

 peak wave height pattern. (The velocity heads were computed using 

 McCowan's solitary wave theory.) The linear trend in Figure D-4 indicates 

 that simple additive wave stagnation effects dominate the measured pat- 

 terns at these two piles with relatively shallow channels. Also, there 

 is little difference in test results with the two geometrically similar 

 piles of different size. 



2. Tests with Closely-Spaced Circular Piles . 



Some tests were performed with two circular piles centered side-by- 

 side in the 1. 5-foot -wide wave tank, primarily to investigate effects 

 of pile confinement. Center-to-center separations were 6 or 9 inches 

 (0.15 or 0.23 meter), the two test piles sometimes had unequal diameter, 

 and a wave pulse including one dominant crest was used. Electrical gages 

 recorded the waveforms 2 feet (0.61 meter) in front of and behind the 

 piles, and the peak waterlines on the piles were recorded by erosion of 

 a powder deposit or wetting of a paper sleeve. The recorded peak water- 

 lines show complicated variability, especially with piles of unequal 

 diameter (Fig. D-5). These tests were basically extraneous to the present 

 study, and no effort was made to interpret the resulting data. 



3. Previously Reported Data of Unsatisfactory Quality . 



Some data presented in Galvin and Hallermeier (1972) and in Figures 

 20, 27, and 28 of this report did not survive the consistency test 

 (App. C) . These data sets are of lower quality than those shown in 

 Appendix C, but are valuable in illustrating qualitative trends. For 

 completeness, the plots on pages 173 to 183 are presented in the standard 

 format used in Appendix C. 



169 



