period (7), wave height (fl), and data length (in 90-sec block, each block 

 corresponding to data collected at one elevation) are listed in Table 11-2. 



Table 11-3 



Matrix Showing the Combination 



of Wave Period and Wave Height in the LDV Data Set 





7=3 sec 



4.5 sec 



8 sec 



H = 0.2 m 



P 





P 



0.4 m 



- 





P 



0.5 m 



- 



- 



PP 



0.6 m 



P 



F 



- 



0.7 m 



PR 



F 



P 



0.8 m 



P 



- 



- 



F: Monochromatic waves, instruments at a fixed elevation (2 = 4 cm). 

 P: Monochromatic waves, instruments in vertical profiling operation. 

 R: Random waves, instruments in vertical profiling operation. 

 -: No measurements. 



Data Analysis 



Methods 



The quantities to be presented in this report are: phase-averaged velocities, 

 phase-averaged turbulent intensities, and phase-averaged sediment concen- 

 tration. These quantities are derived as follows. 



Velocities. For monochromatic waves, which represent the bulk of the 

 data obtained, velocities are decomposed as 



u = U + <u> + u' 



(11-3) 



where 



u = measured velocity 



U = mean drift velocity 



< u > = phase-averaged wave velocity 



u ' = turbulent velocity 



The phase averages are constructed from concatenated time series from dif- 

 ferent profiles, e.g., for 8-sec waves, 11 cycles per profile, times four profiles 

 per run (Run S0609) would produce a phase average over 44 waves. For this 

 example, it follows that the error of the phase-averaged velocity would be 



Chapter 1 1 LDV in the Bottom Boundary Layer 



221 



