The pipe model and wave gage were mounted in a glass-walled part 

 of the tank near the middle of the wave channel to facilitate the vis- 

 ual observation of the phenomenon being studied. For each bottom 

 clearance tested, a series of runs was made with waves generated at 

 19 different wave periods, covering a range of 0.95 to 2.5 seconds. 

 Seven wave heights were generated for each wave period, ranging up to 

 0.34 foot (10.4 centimeters). 



After these runs were completed, the pipeline was set at another 

 bottom clearance, and the procedure was repeated. Seven bottom clear- 

 ances were tested for each wave condition, ranging from 0.001 foot, 

 1/16, 1/8, 3/16, 1/4, 1, and 2 inches (0.305, 1.59, 3.18, 4.76, and 

 6.35 millimeters, 2.54 and 5.08 centimeters], respectively. The mini- 

 mum clearance tested (0.001 foot) was that which placed the pipe sec- 

 tion as close to the bottom as possible without touching the bottom 

 when the waves passed over it. This was necessary to' measure ariy down- 

 ward forces exerted on the pipe section due to the wave action. The 

 2-inch bottom clearance placed the pipe section far enough from the 

 bottom so that the vertical lift forces were insignificant. 



These experiments were carried out with a 4-inch-diameter (10.16 

 centimeters) test cylinder. The experiments were repeated with pipe 

 sections of 2-, 2h- , and 3-inch (5.08, 6.35, and 7.62 centimeters) 

 diameters, but only three bottom clearances were tested--0.001 foot, 

 1/8 inch, and 1/4 inch. The wave conditions covered the same range of 

 wave heights and periods, but were not quite as extensive in number. 



In addition to the vertical force measurements, a series of experi- 

 ments was performed to measure the horizontal forces acting on the pipe 

 section, so that the resultant wave-induced force could be determined 

 throughout the entire wave cycle for several of the experimental condi- 

 tions tested. Only the 4-inch-diameter test cylinder was used in these 

 experiments, since the corresponding vertical experiments were the most 

 extensive for the 4-inch cylinder. The horizontal forces were measured 

 by rotating the force transducer 90° so that it was sensitive only to 

 forces acting in the horizontal direction. The calibration procedure 

 was the same as described above for the vertical force measurements 

 except that the system of pulleys was rearranged so that the calibration 

 weights exerted forces in the horizontal direction only. 



All seven of the bottom clearances used in the vertical experiments 

 were also used in the horizontal tests. The wave periods covered the 

 same range as the vertical experiments, but only 6 of the 19 wave peri- 

 ods were used--0.95, 1.25, 1.5, 1.85, 2.25, and 2.55 seconds. Two of 

 the seven wave heights corresponding to each wave period in the vertical 

 experiments were used in the horizontal tests. 



The Stillwater depth was held constant at a depth of 2 feet through- 

 out the two-dimensional tests. 



50 



