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Tidally-induced flow structure over intertidal flats

Tidally-induced flow structure over intertidal flats
Tidally-induced flow structure over intertidal flats
Previous investigations have assumed that a significant linear relationship between uz-lnZis sufficient to define a logarithmic velocity profile given by the von Kármán–Prandtl equation. However, it is demonstrated here that such a criterion alone is insufficient.

An internal consistency analysis is developed to establish realistic logarithmic velocity profiles, in the estimation of boundary layer parameters associated with intertidal flat environments. The analytical procedure includes: (i) onward linear regression, to establish the relationship between apparent u*values and near-bed current speeds, uz (here, the observed u50 is used); (ii) an assessment of the constant and correlation coefficient within the u*–uz relationship; (iii) calculation of z0 and C50 values, on the basis of the slope of the regression line; and (iv) undertaking a comparison between the derived z0 and C50 and those obtained using the instantaneous velocity profiles. The internal consistency is shown to be enhanced if the data are filtered, before a more detailed analysis.

This approach is applied to the analysis of 192 current velocity (gradient rig) data sets collected from the intertidal flats of the Loughor Estuary and Swansea Bay (South Wales), and The Wash (eastern England). Overall, less than 40% of the data sets are logarithmic in character, with variations between the various stations. Nevertheless, boundary layer parameters were determined for most locations. Non-logarithmic profiles on intertidal flats are considered to be caused by: (i) rotary tidal currents; (ii) wind effects; (iii) wave action and other short-period oscillations; and (iv) topographically-induced secondary flows. Measurement errors can lead also to deviations from an ‘idealized’ logarithmic profile.
logarithmic velocity profile, boundary layer parameters, onward linear regression, internal consistency analysis, intertidal flats, U.K.
0272-7714
233-250
Collins, M.B.
3b70278b-0004-45e0-b3c9-0debdf0a9351
X. Ke, X.
54fad401-9b9f-4dea-b66d-ac5d3503e2c2
Gao, S.
29a7360f-d8cc-4f08-99f4-78262d628c46
Collins, M.B.
3b70278b-0004-45e0-b3c9-0debdf0a9351
X. Ke, X.
54fad401-9b9f-4dea-b66d-ac5d3503e2c2
Gao, S.
29a7360f-d8cc-4f08-99f4-78262d628c46

Collins, M.B., X. Ke, X. and Gao, S. (1998) Tidally-induced flow structure over intertidal flats. Estuarine, Coastal and Shelf Science, 46 (2), 233-250. (doi:10.1006/ecss.1997.0260).

Record type: Article

Abstract

Previous investigations have assumed that a significant linear relationship between uz-lnZis sufficient to define a logarithmic velocity profile given by the von Kármán–Prandtl equation. However, it is demonstrated here that such a criterion alone is insufficient.

An internal consistency analysis is developed to establish realistic logarithmic velocity profiles, in the estimation of boundary layer parameters associated with intertidal flat environments. The analytical procedure includes: (i) onward linear regression, to establish the relationship between apparent u*values and near-bed current speeds, uz (here, the observed u50 is used); (ii) an assessment of the constant and correlation coefficient within the u*–uz relationship; (iii) calculation of z0 and C50 values, on the basis of the slope of the regression line; and (iv) undertaking a comparison between the derived z0 and C50 and those obtained using the instantaneous velocity profiles. The internal consistency is shown to be enhanced if the data are filtered, before a more detailed analysis.

This approach is applied to the analysis of 192 current velocity (gradient rig) data sets collected from the intertidal flats of the Loughor Estuary and Swansea Bay (South Wales), and The Wash (eastern England). Overall, less than 40% of the data sets are logarithmic in character, with variations between the various stations. Nevertheless, boundary layer parameters were determined for most locations. Non-logarithmic profiles on intertidal flats are considered to be caused by: (i) rotary tidal currents; (ii) wind effects; (iii) wave action and other short-period oscillations; and (iv) topographically-induced secondary flows. Measurement errors can lead also to deviations from an ‘idealized’ logarithmic profile.

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More information

Published date: February 1998
Keywords: logarithmic velocity profile, boundary layer parameters, onward linear regression, internal consistency analysis, intertidal flats, U.K.

Identifiers

Local EPrints ID: 72284
URI: http://eprints.soton.ac.uk/id/eprint/72284
ISSN: 0272-7714
PURE UUID: d68ab8a9-83a6-413f-869a-33eed9d209e2

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Date deposited: 04 Feb 2010
Last modified: 08 Nov 2021 17:14

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Contributors

Author: M.B. Collins
Author: X. X. Ke
Author: S. Gao

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