TM No. 377 



10. r: The linear correlation coefficient defined by equation ( 111=29). 



11. L,H.T: The (eye) estimate of the wave length, wave-height, and 

 period of the wind waves (sea) and swell. These values are only indicated as 



a guide, and are by no means an accurate statistical estimate of the parameter. 



12. ©: The estimated direction of the wind waves (sea) and swell. 



13. Wind: Wind speed (m sec"^-) and direction from which it is blowing. 

 Ik. D: Doubtful data. 



NOTE: For BBELS-5 and 7, the number of lags M = 32; for all other series, M = 50, 



Wave Gauge System Observations 



The Coastal Engineering Research Center (formerly the Beach Erosion Board) 

 maintains aboard the BBELS from March through September a relay type step 

 resistance wave gauge. This instrument provides a record of the height of the 

 free surface, designated by *»){£) > at a fixed location in the ocean. During 

 the months of operation, the wave gauge is programmed to record y for specific 

 time intervals during the day. Unfortunately, during most of the wave meter 

 observations (spring and summer of 1965). the wave gauge was inoperative because 

 of biological fouling problems. However, some wave staff records were obtained 

 during or near the time of wave meter measurements, which allowed a rough com- 

 parison of the two wave monitoring systems. 



The wave gauge operates on the principle of an electrolyte (sea water) 

 completing an electrical circuit between a power supply and a relay coil, 

 which (when engaged) bypasses a fixed resistance. Figure TV-19 is a schematic 

 representation of this system. Switching of the relays 1, 2, 3 • • • occurs 

 in sequence when the free surface mades contact with copper contacts linearly 

 spaced on the vertical staff. As the relays are made, the resistances R^, R , 

 Ro • . . are eliminated from the circuit, and the voltage on the recorder 

 increases proportionally. Thus, as the water level rises and falls with the 

 passing waves, the voltage V(t) fluctuates, presenting (with proper calibration) 

 a linear voltage analog of the time-variable free surface oscillation yftj> 



The actual wave staff containing the copper contacts was fastened to the 

 south side of the southeast leg of the BBELS. The staff is composed of nine 

 sections, each 153 cm long. The copper contacts on the bottom three sections 

 are 7-5 cm apart, wnereas on the top six sections the contacts are 30.5 cm apart. 

 This spacing arrangement permitted relatively high resolution for waves of aver- 

 age and a lower resolution for the larger waves. This recording system was 

 housed in the laboratory of the BBELS. The recording was done on both an ink- 

 pen strip chart recorder and on a magnetic tape recorder system. 



92 



