The spectral components S u (0) and S w (0) are excluded from the inte- 

 grations. 



c. Peak spectral periods 7^ and T^ of the velocity components defined 

 as the reciprocal of the frequency containing the greatest energy. 



Time series analysis. The time series analysis was performed with a zero- 

 upcrossing definition of a wave. A wave is defined between two upward 

 crossings of the water surface about the mean water elevation. The upcross- 

 ing definition was chosen because the saw-tooth shape of the nearshore wave 

 profile gives distinct upward crossings, whereas downcrossings vary from 

 wave to wave. The wave height H of an individual wave is defined as the 

 difference between the highest and lowest water elevation between two zero 

 upcrossings. The wave period Tof an individual wave is defined as the time 

 between zero upcrossings. Very small waves (H < 0.6 cm), associated with 

 small surface variations near the mean water elevation, were not identified as 

 individual waves. These very small waves were included as part of the pre- 

 ceding wave. The time series parameters calculated for the resistance wave 

 staffs are: 



a. Mean water elevation 



if = -En. 0-9) 



1 N 



where ij is the measured water elevation and N is the number of data 

 points. 



b. Standard deviation of the water surface 



Eft - n) O-iO) 



N N - 1 



c. Skewness of the water surface 



\3 



64 



. Ed - ti) (3 _ u) 



3 o 3 



which is a measure of the horizontal asymmetry of the waves. 



d. Kurtosis of the water surface 



= Ed - ^ (3-12) 



o 4 



which is a measure of the peakedness of the waves. 



Chapter 3 SUPERTANK Hydrodynamics 



