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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.

Descriptions

Resource type

Dataset

Contributors

Creator: Hardy, Richard ¹
Contact person: Hardy, Richard ¹
Data collector: Hardy, Richard ¹

¹ Durham University, UK

Funder

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

Keyword

Computational fluid dynamics
Alluvial Dunes
Turbulence
Large Eddy Simulation

Subject

Fluvial Geomorphology

Location

Language

Cited in

Identifier

ark:/32150/r12z10wq23s
doi:10.15128/r12z10wq23s

Rights

Creative Commons Attribution 4.0 International (CC BY)

Publisher

Durham University

Date Created

LES simulations completed in 2019

File Details

Depositor

R. Hardy

Date Uploaded

15 February 2021, 10:02:56

Date Modified

15 February 2021, 11:02:09

Audit Status

Audits have not yet been run on this file.

Characterization

File format: zip (ZIP Format)

Mime type: application/zip

File size: 304881156

Last modified: 2021:02:15 10:26:05+00:00

Filename: Data.zip

Original checksum: 141085ab3c69a709f1ae21eab57048f5