118 



LDV location 



gauge 2 



Wave maker 



,0.17m 



t t 



gauge 3 gauge 1 



Plan 



V \ 



-J # ► 



Figure 5.37: Layout of array in flume 



wave maker. At a depth of 0.35m, the approximate wave celerity (y/gh) is 1.8m/s. As 

 the measuring location is located 9m from the beach, it takes about 10s for the waves 

 to travel from the measurement location to the beach, and for the reflected waves 

 to travel back to the study location. Thus, the first 10s of the record are assured of 

 being uncontaminated by reflection from the beach. Using only the beginning of the 

 record also prevents a Stokes drift induced return current to be established, and so 

 the Eulerian current is taken to be zero. 



5.5.2 Laboratory Results 



Figure 5.38 shows a sample wave taken from an irregular wave record measured 

 in the flume. The waves were generated with a target TMA spectrum (Bouws et al. 

 1985) with a peak period of 2.5s and mean wave height of approximately 12cm. The 

 water depth was 0.35m, with the velocities measured by the LDV at an elevation of 

 0.05m below the mean water level. The solid lines on figure 5.38 are the horizontal and 

 vertical velocities as measured by the LDV. The circles are the velocities predicted by 

 the LFI method at the center of each computed window. The solid line in the water 

 surface plot is the measured elevation at wave rod 2, at the same x coordinate as the 

 center of the array. The circles are the water surface elevations at the center of the 



