117 



46 m 



0.46 m 



m 



18 m 



Beach with horsehair matting 



1 



Plan 



ll^^ 



Elevation 



Wave board 



(not to scale) 



Figure 5.36: Schematic of wave flume 



Hmo/h = 0.1 up to about 15% for Hmo/h = 0.4 (where Hmo is the incident spectral 

 significant wave height and h is the water depth) (Sultan 1992; Sultan and Hughes 

 1993). 



The water surface was measured by capacitance wave rods, calibrated with a cubic 

 calibration function. The velocity data were collected using a Dantek laser Doppler 

 velocimeter (LDV) system operated in the backscatter mode. The LDV system fea- 

 tured a 2-watt argon-ion laser equipped with a fiber-optic probe that measures two 

 orthogonal water velocity components (horizontal and vertical). Velocity data were 

 converted in real time to engineering units (m/s) and written to a computer file 

 simultaneously with the wave rod data. 



The wave rods and LDV were placed near the middle of the flume, with the wave 

 rods arranged in an equilateral triangle with leg length of 0.17m (see Fig. 5.37). The 

 LDV was situated to measure the horizontal and vertical velocities at the center of the 

 array, at a variety of vertical elevations. The flume was allowed to reach quiescence 

 in between runs, and the waves were measured for only a short time after starting the 



