Turbulence Measurements from Compliant Moorings. Part II: Motion Correction

Acoustic Doppler velocimeters (ADVs) are a valuable tool for making high-precision measurements of turbulence, and moorings are a convenient and ubiquitous platform for making many kinds of measurements in the ocean. However, because of concerns that mooring motion can contaminate turbulence measure...

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Bibliographic Details
Published in:Journal of atmospheric and oceanic technology 2017-06, Vol.34 (6), p.1249
Main Authors: Kilcher, Levi F, Thomson, Jim, Harding, Samuel, Nylund, Sven
Format: Article
Language:English
Subjects:
Acoustic measurement
Alternative energy
Boundary layers
Contamination
Deep sea moorings
Dissipation
Doppler sonar
Energy industry
Estimates
Fluid dynamics
Inertial sensing devices
Isotropic turbulence
Kolmogorov theory
Laboratories
Mooring
Mooring systems
Motion compensation
Movement
Profilers
Reynolds stresses
Sensors
Spectra
Tidal inlets
Turbulence measurement
Velocimetry
Velocity
Velocity measurement
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Summary:Acoustic Doppler velocimeters (ADVs) are a valuable tool for making high-precision measurements of turbulence, and moorings are a convenient and ubiquitous platform for making many kinds of measurements in the ocean. However, because of concerns that mooring motion can contaminate turbulence measurements and that acoustic Doppler profilers make middepth velocity measurements relatively easy, ADVs are not frequently deployed from moorings. This work demonstrates that inertial motion measurements can be used to reduce motion contamination from moored ADV velocity measurements. Three distinct mooring platforms were deployed in a tidal channel with inertial-motion-sensor-equipped ADVs. In each case, motion correction based on the inertial measurements reduces mooring motion contamination of velocity measurements. The spectra from these measurements are consistent with other measurements in tidal channels and have an slope at high frequencies-consistent with Kolmogorov’s theory of isotropic turbulence. Motion correction also improves estimates of cross spectra and Reynolds stresses. A comparison of turbulence dissipation with flow speed and turbulence production indicates a bottom boundary layer production-dissipation balance during ebb and flood that is consistent with the strong tidal forcing at the site. These results indicate that inertial-motion-sensor-equipped ADVs are a valuable new tool for making high-precision turbulence measurements from moorings.
ISSN:0739-0572
1520-0426
DOI:10.1175/JTECH-D-16-0213.1">