PART II: LABORATORY SETUP AND TECHNIQUES USED 



7. To date, 205 two-dimensional laboratory tests of reef breakwaters 

 have been completed. These tests were conducted in a 61-cm-wide channel 

 within CERC's 1.2- by 4.6- by 42.7-m tank (Figure 1). All tests were 



5(m) 



o DENOTES WAVE GAGE LOCATION 



WALL OF WAVE TANK 



TO WAVE 



1 ON 15 



I GRAVEL WAVE ABSORBER 

 BEACH 



: 

 SHOALING SLOPE | 



GjAVJLJ«AJiEJiBS^R|EOEACHd 

 EFlftANNEL " ""wauT 



oo o ^_ -iEEj ° ° ABSORBER 



REEF _P0N0!NG, REL IEF CHANNEL 



BREAKWATER W 

 GRAVEL WAVE ABSORBER BEACH 



AUXILIARY CHANNEL 



"MATERIAL] 



GRAVEL WAVE 

 ABSORBER BEACH 



GRAVEL WAVE ABSORBER BEACH 



WALL OF WAVE TANK 



PLAN VIEW 



Figure 1 . Plan view of wave tank and test setup 



conducted with irregular waves. The spectra used had wave periods of peak 

 energy density T * ranging from about 1.45 to 3.60 sec, and water depth at 

 the structure d ranged from 25 to 30 cm. Signals to control the wave blade 

 were stored on magnetic tape and transferred to the wave generator through a 

 computer data acquisition system (DAS) . For this study four files were stored 

 on the tape which could produce a spectrum with a distinct period of peak 

 energy density. Table 1 gives the nominal period of peak energy density for 

 each file. 



8. If there were no attenuation of the signal to the wave generator, 

 the files used were intended to produce a saturated spectrum at all frequences 

 above the frequency of peak energy density for the water depth at the wave 

 blade. For frequencies lower than those of the peak, the energy density de- 

 creased rapidly. This procedure produced a spectrum of the Kitaigorodskii 

 type as described by Vincent (1981). The amplitude of the signal to the wave 

 generator was attenuated by a 10-turn potentiometer in a voltage divider 



* For convenience, symbols and unusual abbreviations are listed and defined 

 in the Notation (Appendix C) . 



