TR No. 22 
Additional measurements have been made by Grant and Stewart (5) 
of the turbulence spectra in a tidal current (Georgia Straight and 
Juan De Fuca Straight) near the water surface in the presence of sur- 
face waves and noise. The results of the previous measurements were 
used to determine values of € , although the energy dissipation spectra 
could not be calculated because of the interference. 
Complementary measurements to those of Grant et al were made over 
the low wave number anisotropic range of the spectrum from approximately 
0.01 meters™+ to 2.0 meters~1 by Bowden (6) and by Bowden and Howe (4). 
The jactrument used. was an electromagnetic flowmeter. Although the 
Kolmogoroif hypothesis does not apply to the low wave number range, the 
spectra obtained from the measurements by Bowden and Howe were reported 
to follow a power law similar to that predicted by the Kolmogoroff 
hypothesis, but with an exponent of the order of -1.3 instead of -5/3 
for wave numbers from approximately 0.001 om=+ to 0.01 em7+, 
Shonting (8, 9, 15, 16) has used a ducted impeller ocean current 
meter to make measurements of the particls motions in ocean waves to 
frequencies of 2,5 Hz. The results demonstrated the potential of the 
current meter for measuring relatively high frequency and/or wave number 
oceanographic turbulence. The hot film anemometer used previously (2,3,5) 
is a complex instrument requiring considerable electronic equipment to 
obtain an output suitable for data analysis. In addition, difficulties 
are encountered in using the hot film anemometer probe at sea because of 
the corrosive and electrolytic properties and the high level of contamina- 
tion of sea water. The advantages of the ducted impeller current meter in 
comparison are simplicity, sturdiness, and reliability, desirable characteris- 
tics in an oceanographic instrument; the output of the current meter is of the 
appropriate form for digital spectral analysis with respect to wave number. 
The objectives of the measurements reported herein, then, are to; (1) obtain, 
using the current meter, additional turbulence spectra from a tidal current 
which can be compared with the spectra obtained using the hot film anemometer 
in order to determine the applicability and/or the limitations of the current 
meter for measuring oceanographic turbulence; (2) provide additional experi- 
mental confirmation of the Kolmogoroff hypothesis. 
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