Structure 1, the shore-parallel breakwater (Figures 5 and 6), was placed
offshore of the beach in a region with shore-parallel contours. The breakwater
extended 9.1 m (30 ft) to the sidewall of the model. The wave generator was
initially set parallel to the shoreline, then moved to a 20-deg angle with the
shoreline, positioned to enhance increased energy propagation behind the
breakwater. Note the partition across the channel that isolated the bay from the
ocean. Data collection consisted of wave heights and direction from gauges on
movable racks at 20 locations and at 10 fixed locations. Thirty locations were
sampled simultaneously for a given instrument arrangement. There were five
arrangements of the movable gauge racks for the offshore breakwater, for a total
of 100 gauge locations shoreward of the breakwater. Five fixed wave gauges
were located on line with the offshore breakwater defining the incident wave that
would refract-diffract behind the breakwater. Five additional gauges were placed
at the wave generator to define deeper water wave conditions and ensure
consistent wave generation. Also placed on the wave gauge rack were two
ADVs, which were analyzed to define wave direction. This portion of the data
collection was to provide a crosscheck of the wave direction measurements made
through analysis of video photography from multiple cameras to determine wave
direction.
Structure 2, the dogleg jetty, is shown in Figure 7 with its gauge arrangement
depicted in Figure 8. The gauge arrangements of Structures 3 and 4 are shown in
Figures 9 and 10, respectively, and photographs of the setups are shown in
Figures 11 and 12, respectively. Table 2 summarizes the experiments. Horsehair
wave absorber was located on the outside of Structures 1, 2, and 4 to minimize
reflection back to the wave generator and ocean basin region. For Structures 1
and 2, the absorber was terminated 0.9 m (3 ft) from the tip of the structure. See
Figure 7 for absorber location. For Structure 4, the absorber was placed on the
oceanside of each of the parallel jetties, extending to the tip (Figure 12). The
absorber extended through the water surface. Chapter 4 contains additional
details for each structure.
10
Chapter 2 Laboratory Facility, Equipment, and Experiment Design
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