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Flow structures over fixed 2D bedforms in transient states
Unsworth, C.A.; Parsons, D.R.; Reesink, A.J.H.; Best, J.L.; Ashworth, P.J.; Hardy, R.J. (2013). Flow structures over fixed 2D bedforms in transient states, in: Van Lancker, V. et al. (Ed.) MARID 2013: Fourth International Conference on Marine and River Dune Dynamics. Bruges, Belgium, 15-17 April 2013. VLIZ Special Publication, 65: pp. 265-270
In: Van Lancker, V.; Garlan, T. (Ed.) (2013). MARID 2013: Fourth International Conference on Marine and River Dune Dynamics. Bruges, Belgium, 15-17 April 2013. VLIZ Special Publication, 65. Royal Belgian Institute of Natural Sciences/SHOM/Flanders Marine Institute (VLIZ): Oostende. ISBN 978-2-11-128352-7. 338 pp., more
In: VLIZ Special Publication. Vlaams Instituut voor de Zee (VLIZ): Oostende. ISSN 1377-0950, more

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Keyword
    Marine

Authors  Top 
  • Unsworth, C.A.
  • Parsons, D.R.
  • Reesink, A.J.H.
  • Best, J.L.
  • Ashworth, P.J.
  • Hardy, R.J.

Abstract
    Flow processes measured in the laboratory over fixed, 2D or 3D bedforms have mostly been conducted at one flow depth and with bedform dimensions set by scaling laws based upon “equilibrium” flow conditions. These results thus have limited applicability to many natural situations where bedforms and flow fields are co-evolving at different rates in response to transient conditions, such as changes in flow depth and flow discharge associated with a flood. The research presented herein investigates flow processes over 2D fixed bedforms under a range of non-equilibrium, transient, states in order to quantify the spatio-temporal changes in turbulence associated with steady conditions that are set at nonequilibrium depths and velocities. Flow field information was obtained at steady states for a range of flow depths and mean flow velocities, mimicking conditions during the transient evolution of flow and bedforms during a flood wave. This allowed quantification of flow fields over bedforms under transient boundary conditions, including shear stress profiles and the spatial variation in the dynamics of the separation zone. These findings provide data for a preliminary assessment of the link between sediment transport lag and transient flow dynamics, and facilitate an analysis of the implications of variable dune height: flow depth for flood wave propagation and bedform response.

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