Analysis of Velocity Measurements at NOTS Pier on San Clemente Island
NAVAL UNDERSEA WARFARE CENTER DIV NEWPORT RI
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This report describes oceanographic observations at NOTS Pier on San Clemente Island, CA. Velocity measurements were made to assess the suitability of NOTS Pier for testing ocean turbulence sensors. Measurements at NOTS Pier on San Clemente Island off the coast of Southern California show that the water velocities there consist of tidal currents and oscillations caused by surface waves. Tidal currents are parallel to the shoreline with frequencies that are mixed diurnal and semidiurnal with an rms amplitude of approximately 8 cms. Ocean swells 10- to 12-s period and wind waves 3- to 5-s period induce periodic horizontal and vertical velocities with rms amplitudes of 5 cms and 1 cms, respectively, under quiet conditions. Direct measurement of small-scale velocities with high-frequency current meters indicates that the velocity field under the pier is consistent with anisotropic turbulence. Using a model of frozen field turbulence in an oscillating mean flow, estimates of the turbulent dissipation rate are Ew 1.1 x 10expn -5m2s3 based on the horizontal velocity spectrum and Ew 1.1 x 10expn -6m2s3 for the vertical.
- Physical and Dynamic Oceanography
- Acoustic Detection and Detectors