Drag Coefficients of Oceanographic Mooring Components.

Finke, M. and Siedler, Gerold (1986) Drag Coefficients of Oceanographic Mooring Components. Open Access Journal of Atmospheric and Oceanic Technology, 3 (2). pp. 255-264. DOI 10.1175/1520-0426(1986)003<0255:DCOOMC>2.0.CO;2.

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Abstract

The inclination of oceanographic mooring lines due to current drag causes errors in time series observations of currents and temperatures. The prediction of this effect requires knowledge of the drag coefficients for the mooring components. Drag coefficients, known for simple geometric shapes such as spheres or cylinders, are commonly used for mooring response computations. Selected mooring components (buoyancy elements and instruments) were tested in a tow tank to determine their actual drag coefficients. Over the Reynolds Number range, typical of oceanic conditions, deviations of the drag coefficient up to 50% are found when compared with the appropriate simple geometric shape coefficients. A set of model moorings and model current profiles is used to determine the resulting changes in component depth level and displacement. The changes in horizontal displacement of the upper part of the mooring are on the order of 10% in extreme cases and 1% under typical conditions. Their effects on current measurements will usually be negligible. However, the related vertical displacements are on the order 100 to 10 m. Such vertical displacements may carry instruments to depth levels where currents and particularly thermocline temperatures are sufficiently different from the intended level to cause errors in the time series observations.

Document Type: Article
Keywords: Physical oceanography
Research affiliation: OceanRep > GEOMAR > FB1 Ocean Circulation and Climate Dynamics > FB1-PO Physical Oceanography
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1175/1520-0426(1986)003<0255:DCOOMC>2.0.CO;2
ISSN: 0739-0572
Date Deposited: 25 Sep 2012 12:17
Last Modified: 01 Jun 2018 09:19
URI: http://oceanrep.geomar.de/id/eprint/15383

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