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The influence of three-dimensional topography on turbulent flow structures over dunes [dataset] Open Access

Dunes are the most prevalent bedforms in sand-bedded rivers and their morphology typically comprises of multiple scales of three-dimensional topography. However, our understanding of flow over dunes is predicated largely on two-dimensional models, a condition which is rare in nature. Here, we present results of Large Eddy Simulations over a static, three-dimensional dune field, using a two- and three- dimensional topographic realisation, to investigate the interaction between bed topography and turbulent flow structures. We show that flow over two-dimensional bedforms increases the velocity over the stoss slope that reduces the size of the leeside separation zone. Flow over three-dimensional bedforms generates approximately 70% less form drag and is 150% more turbulent, with twice as many vortices that are longer, wider and taller. Turbulence is dominated by hairpin shaped vortices and Kelvin-Helmholtz instabilities that interact with the bed in the brink point region of the dune crest and down the lee slope, and generate high shear stresses for long durations. These finding highlight how the size, morphology and stacking of coherent flow structures into larger flow superstructures may be critical in sediment entrainment, and dictate the relationship between event duration and magnitude that drive sediment impulses at the bed and will ultimately lead to an increased three-dimensionality in bedform morphology.


Resource type
Creator: Hardy, Richard 1
Contact person: Hardy, Richard 1
Data collector: Hardy, Richard 1
1 Durham University, UK
Natural Environment Research Council
Research methods
A Large Eddy Simulation model was developed and applied to study turbulent flow over a three dimensional dune field
Other description
This is the data associated with 'The influence of three-dimensional topography on turbulent flow structures over dunes' under review in Journal of Geophysical Research – Earth Surface
Computational fluid dynamics
Alluvial Dunes
Large Eddy Simulation
Fluvial Geomorphology
Cited in
Creative Commons Attribution 4.0 International (CC BY)

Durham University
Date Created
LES simulations completed in 2019

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R. Hardy
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15 February 2021, 11:02:09
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