[XFFLISION OF OCEANIC HEAT AND MOMENTUM
355
spended at 20-120 m in the surface layer from the Scripps stable platform
FLIP and towed in a mixed layer at about 20 m depth off San Diego. In part.
the experiments were intended to develop reliable instruments and
techniques for turbulence measurements at sea, as well as make the measurements themselves.
2. MEASUREMENT TECHNIQUES
2.1. Towing Methods
A major source of false velocity signal for a sensor towed by a ship is the
surface moticn transmitted through the suspending cable. Various methods
might be used to reduce the amount of surface motion transmitted to the
towed body such as a servo winch controlled by a pressure sensor on
the body to maintain constant depth (Nasmyth, 1970), using springs or
elastic material on the cable to act as a low pass filter of ship's motion, or by
attaching lifting and/or suppressing bodies to the cabk. Ounidov describes
an arrangement with the sensors mounted above a deprcssor and below a
lifting body designed to keep the package on a vertical cable at constant
depth (Ozmidov and Belyaev, 1972; see also Omidov, 1971).
The method employed for the prtscnt towed measuTements was to take
advantage of the fact that the ship fnduced motion is at relatively low
frequencies compared to that of the smallest scab turbuknco and temperature fluctuations. A typical wave frequency at sea is 0.1 Hz, which is small
compared to either 1 Hz, corresponding to 1 m maximum length scale of the
turbulence at a towing speed of 1 m/sec, or lo00 Hz, corresponding to a
viscous scale of 1 mm. A 600-lb 5-in. diameter steel cylinder filled with lead
was provided with a 2 x 5 ft fin and upstream instrument support. This
" fish " was supported by a 600-m long & in. diameter double lay armored
cable on a winch. Four conductors inside the cable were used to transmit
information to the laboratory in the ship. Further inhrmation concerning
the arrangement during the Cromwell Current measurements is given elsewhere (Williams and Gibson, 1974; Gibson and Williams, 1973). Using a
vibrotron pressure sensor it was found that the vertical fish motion was in
phase with the surface waves and of smaller amplitude for depths of about
100 m at towing speeds of about 1 m/sec.
2.2. Universal Similarity Theory
Estimates of the turbulence and temperature dissipation rates E and were
obtained by fitting the measured high frequency veiocity and temperature
spectra to forms predicted by universal similarity hypotheses based on Kolmogoroff and Batchelor length and time scales (Gibson, 1968). The actual
355
spended at 20-120 m in the surface layer from the Scripps stable platform
FLIP and towed in a mixed layer at about 20 m depth off San Diego. In part.
the experiments were intended to develop reliable instruments and
techniques for turbulence measurements at sea, as well as make the measurements themselves.
2. MEASUREMENT TECHNIQUES
2.1. Towing Methods
A major source of false velocity signal for a sensor towed by a ship is the
surface moticn transmitted through the suspending cable. Various methods
might be used to reduce the amount of surface motion transmitted to the
towed body such as a servo winch controlled by a pressure sensor on
the body to maintain constant depth (Nasmyth, 1970), using springs or
elastic material on the cable to act as a low pass filter of ship's motion, or by
attaching lifting and/or suppressing bodies to the cabk. Ounidov describes
an arrangement with the sensors mounted above a deprcssor and below a
lifting body designed to keep the package on a vertical cable at constant
depth (Ozmidov and Belyaev, 1972; see also Omidov, 1971).
The method employed for the prtscnt towed measuTements was to take
advantage of the fact that the ship fnduced motion is at relatively low
frequencies compared to that of the smallest scab turbuknco and temperature fluctuations. A typical wave frequency at sea is 0.1 Hz, which is small
compared to either 1 Hz, corresponding to 1 m maximum length scale of the
turbulence at a towing speed of 1 m/sec, or lo00 Hz, corresponding to a
viscous scale of 1 mm. A 600-lb 5-in. diameter steel cylinder filled with lead
was provided with a 2 x 5 ft fin and upstream instrument support. This
" fish " was supported by a 600-m long & in. diameter double lay armored
cable on a winch. Four conductors inside the cable were used to transmit
information to the laboratory in the ship. Further inhrmation concerning
the arrangement during the Cromwell Current measurements is given elsewhere (Williams and Gibson, 1974; Gibson and Williams, 1973). Using a
vibrotron pressure sensor it was found that the vertical fish motion was in
phase with the surface waves and of smaller amplitude for depths of about
100 m at towing speeds of about 1 m/sec.
2.2. Universal Similarity Theory
Estimates of the turbulence and temperature dissipation rates E and were
obtained by fitting the measured high frequency veiocity and temperature
spectra to forms predicted by universal similarity hypotheses based on Kolmogoroff and Batchelor length and time scales (Gibson, 1968). The actual