TM No. 377 

 erg cm~3 sec" for Reynolds stresses of 5, 20, and 80 dyne cm" . These values 



are representative of the magnitudes of -pu'w' obtained with the OMDUM III 

 system at depth ranges from to k meters (see table IV-2). 



Positive values of u indicate a mean current flowing in the +x direction, 

 defined as the direction of the wind wave propagation. Values of ^**/&Tfc ^Q 

 indicate a shear in which the upper velocity U]_ has a larger positive value 

 than the lower velocity ug. Note that in table V-5 all but three shears are 

 positive, giving positive values for the energy dissipation £ w . This is 

 interpreted as the rate of energy transformed from the mean motion into the wave 

 motions. 



Quantities such as fc w have little meaning unless they can be compared with 

 other data. As mentioned in chapter I, Stewart and Grant (1962) presented some 

 estimates of relatively high frequency (or high wave number) turbulent energy 

 dissipation beneath the sea surface in the presence of deep water waves. In 

 brief, they estimated the high wave number spectral contribution to the variance 

 of a one-dimensional velocity record u(t), which was made using a "hot film" 

 flow detector rigidly attached to the bow or suspended from the stern of a 

 vessel underway. Auto-spectra ^«ju were derived from the time series 

 records, using Taylor's hypothesis (see Hinze, 1959)* These were transformed 



lypothesi 



4>u. 00 



to wave number spectra ^\ju (k), where |^ - jw j^—l . 



In theoretical discussions of turbulence, a fundamental parameter associ- 

 ated with the energy of a particular wave number range is defined by Batchelor 

 (1953) as E(k), where: 





(v-59) 







Here u', v* and w* are, as usual, the fluctuating velocities. The experimental 

 measurements of the one-dimensional spectrum ^^ (k) can be applied to the 

 relation: 



( iuMJffa U»* • 



(v-60) 



When the concern is with small scale motions, the dissipation C can be 

 written (see Hinze, 1959) a s: 



158 



