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Sediment Transport of Fine Sand to Fine Gravel on Transverse Bed Slopes in Rotating Annular Flume Experiments

Baar, Anne W.; de Smit, Jaco; Uijttewaal, Wim S. J.; Kleinhans, Maarten G.

Authors

Dr Anne Baar A.Baar@hull.ac.uk
Post-doctoral Research Associate

Jaco de Smit

Wim S. J. Uijttewaal

Maarten G. Kleinhans



Abstract

Large‐scale morphology, in particular meander bend depth, bar dimensions, and bifurcation dynamics, are greatly affected by the deflection of sediment transport on transverse bed slopes due to gravity and by secondary flows. Overestimating the transverse bed slope effect in morphodynamic models leads to flattening of the morphology, while underestimating leads to unrealistically steep bars and banks and a higher braiding index downstream. However, existing transverse bed slope predictors are based on a small set of experiments with a minor range of flow conditions and sediment sizes, and in practice models are calibrated on measured morphology. The objective of this research is to experimentally quantify the transverse bed slope effect for a large range of near‐bed flow conditions with varying secondary flow intensity, sediment sizes (0.17–4 mm), sediment transport mode, and bed state to test existing predictors. We conducted over 200 experiments in a rotating annular flume with counterrotating floor, which allows control of the secondary flow intensity separate from the streamwise flow velocity. Flow velocity vectors were determined with a calibrated analytical model accounting for rough bed conditions. We isolated separate effects of all important parameters on the transverse slope. Resulting equilibrium transverse slopes show a clear trend with varying sediment mobilities and secondary flow intensities that deviate from known predictors depending on Shields number, and strongly depend on bed state and sediment transport mode. Fitted functions are provided for application in morphodynamic modeling

Journal Article Type Article
Publication Date 2018-01
Journal Water Resources Research
Print ISSN 0043-1397
Electronic ISSN 1944-7973
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 54
Issue 1
Pages 19-45
APA6 Citation Baar, A. W., de Smit, J., Uijttewaal, W. S. J., & Kleinhans, M. G. (2018). Sediment Transport of Fine Sand to Fine Gravel on Transverse Bed Slopes in Rotating Annular Flume Experiments. Water Resources Research, 54(1), 19-45. https://doi.org/10.1002/2017wr020604
DOI https://doi.org/10.1002/2017wr020604
Keywords Transverse slope; Sediment transport; Annular flume; Experiments; Bend flow
Publisher URL https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017WR020604

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