Unsteady turbulence measurements in breaking tidal bores including the effect of bed roughness

Docherty, N. J. and Chanson, H. (2011). Unsteady turbulence measurements in breaking tidal bores including the effect of bed roughness. In: Eric Valentine, Colin Apelt, James Ball, Hubert Chanson, Ron Cox, Robert Ettema, George Kuczera, Martin Lambert, Bruce Melville and Jane Sargison, Proceedings of the 34th IAHR World Congress. 34th IAHR World Congress, 33rd Hydrology and Water Resources Symposium and 10th Conference on Hydraulics in Water Engineering, Brisbane, Australia, (1039-1046). 26 June - 1 July 2011.

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Name Description MIMEType Size Downloads
Author Docherty, N. J.
Chanson, H.
Title of paper Unsteady turbulence measurements in breaking tidal bores including the effect of bed roughness
Conference name 34th IAHR World Congress, 33rd Hydrology and Water Resources Symposium and 10th Conference on Hydraulics in Water Engineering
Conference location Brisbane, Australia
Conference dates 26 June - 1 July 2011
Proceedings title Proceedings of the 34th IAHR World Congress
Place of Publication Brisbane, Australia
Publisher Engineers Australia
Publication Year 2011
Sub-type Fully published paper
ISBN 9780858258686
Editor Eric Valentine
Colin Apelt
James Ball
Hubert Chanson
Ron Cox
Robert Ettema
George Kuczera
Martin Lambert
Bruce Melville
Jane Sargison
Start page 1039
End page 1046
Total pages 8
Collection year 2012
Language eng
Abstract/Summary A tidal bore is an unsteady flow motion generated by the rapid water level rise at the river mouth during the early flood tide under appropriate macro-tidal and bathymetric conditions. The present study investigated physically the turbulent properties of breaking tidal bores. The results were based upon some experimental measurements of free-surface fluctuations and turbulent velocities conducted on smooth and rough beds. Using an ensemble-averaging technique, the free-surface fluctuations of breaking tidal bores were characterised. Immediately prior to the roller, the free-surface curved gradually upwards, and the passage of the bore roller was associated with some large water elevation fluctuations. The turbulent velocity measurements were performed at several vertical elevations during the breaking bore. Both the instantaneous and ensemble-averaged velocity data highlighted some strong flow deceleration at all elevations. Close to the bed, the longitudinal velocity component became negative immediately after the roller indicating the existence of a transient recirculation. The vertical velocity data presented some positive, upward motion beneath the roller with increasing maximum vertical velocity at increasing elevation above the bed. The transverse velocity data show some large fluctuations with a non-zero ensemble-average after the roller passage, suggesting some secondary turbulent motion advected behind the bore.
Keyword Tidal bores
Breaking roller
Physical modelling
Bed roughness
Q-Index Code E1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Conference theme - Balance and Uncertainty: Water in a Changing World

Document type: Conference Paper
Collections: School of Civil Engineering Publications
Official 2012 Collection
 
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Created: Sat, 02 Jul 2011, 14:18:13 EST by Hubert Chanson on behalf of School of Civil Engineering