Three-dimensional airflow and sediment transport patterns over barchan dunes

Smith, Alexander B.; Jackson, Derek W.T.; Cooper, J. Andrew G.

doi:10.1016/j.geomorph.2016.10.025

Cited by 38 publications

(38 citation statements)

References 66 publications

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“…Secondary lee slope airflow patterns generated by flow separation at the dune crest and subsequent reattachment flow generate complex eddies and vortices which affect surface shear stress and sediment redistribution (Wiggs, ; Walker & Nickling, ; Parsons et al ., ,b; Cupp et al ., ; Jackson et al ., ,b; Pelletier et al ., ; Smith et al ., ). As more airflow modelling is conducted, the effect of lee side airflow patterns on the initiation of ‘lobe’ and ‘funnel’ flows may become better understood, and a direct link to turbulent airflow and localized slope destabilization may be discovered (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…More recently, the exploration of complex airflow patterns in the lee side of aeolian dunes using high resolution computational modelling has suggested a possible role for turbulent winds disturbing areas of the slipface and increasing the potential to trigger grain flow. For example, secondary lee slope flow patterns generated by flow separation at the dune crest and the subsequent reattachment flow have been observed to produce complex eddies and vortices (Parsons et al ., ,b; Jackson et al ., ,b; Pelletier et al ., ; Smith et al ., ). While the role of these complex airflow patterns in sediment transport on the lee side of a dune is not well‐understood, they may have a significant localized effect on surface shear stress, resulting in sediment redistribution (e.g.…”

Section: Introductionmentioning

confidence: 99%

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Morphometric analysis of slipface processes of an aeolian dune: Implications for grain‐flow dynamics

et al. 2018

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Grain flows are an integral part of sand dune migration; they are a direct response to the local wind regime and reflect complex interactions between localized over-steepening of a dune slipface and complex turbulent airflow on the lee slope. Grain flows are primarily responsible for delivering sediment to the base of a dune, thus driving slipface advancement; yet, there are few constraints on their morphological and spatial characteristics or the amount of sediment that is redistributed by these flows. Using a combination of high-resolution terrestrial laser scanning and video recordings, four distinct grain-flow types are identified based on morphology and area on a dune slipface. Grain-flow morphologies range from small, superficial flows to larger flows that affect greater portions of the slipface, moving significant amounts of sediment. Detailed field observations are presented of the dynamics of lee slopes, including measurements of the initiation location, thickness, magnitude and frequency statistics of grain flows, as well as volume estimates of redistributed sediment for each grain flow observed. High-resolution laser scans enable accurate quantification of bulk sediment transfer from individual grain flows and can be used to study grain flows in a variety of environments. A categorization of grain-flow morphologies is presented that links styles of flows with wind strength and direction, turbulent airflow, sediment deposition and environment.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Morphometric analysis of slipface processes of an aeolian dune: Implications for grain‐flow dynamics

et al. 2018

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“…This increase in δTI can lead to intermittent sediment transport due to the momentum transfer of the overlying turbulent wake zone to the surface near the point of reattachment [ Walker and Nickling , ; Baddock et al ., ]. Our results also show elevated values of δTI on the lee slopes providing elevated erosive potential due to destabilizing concave curvature in mobilizing sediment under low threshold values [ Wiggs et al ., ; Smith et al ., ]. Coherent flow structures are also apparent and are identified by an elevated δTI signature (Figures a–d).…”

Section: Discussionmentioning

confidence: 99%

“…Modeling of the regional airflow conditions across the study site was conducted in OpenFOAM, an opensource CFD modeling software. For the simulations conducted in this study, the Re‐Normalization Group k − ϵ model was implemented because it has relatively low computational costs and the ability to accurately simulate flow conditions in complex three‐dimensional dune environments [ Smith et al , ]. Atmospheric boundary layer (ABL) conditions, specified at the model inlet, are free stream velocity ( U ; equation ), turbulent kinetic energy ( k ; equation ), and energy dissipation ( ϵ ; equation ) [ Richards and Hoxey , ].…”

Section: Methodsmentioning

confidence: 99%

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Quantifying the role of urbanization on airflow perturbations and dunefield evolution

et al. 2017

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Rapid urban development has been widespread in many arid regions of the world during the Anthropocene. Such development has the potential to affect, and be affected by, local and regional dunefield dynamics. While urban design often includes consideration of the wind regime, the potential impact of construction on the surrounding environment is seldom considered and remains poorly understood. In this study, regional airflow modeling during successive stages of urbanization at Maspalomas, Gran Canaria, Spain, indicates significant and progressive flow perturbations that have altered the adjacent dunefield. Significant modifications to the boundary layer velocity, mean wind directionality, turbulence intensity, and sediment flux potential are attributed to the extension of the evolving urban geometry into the internal boundary layer. Two distinct process/response zones were identified: (1) the urban shadow zone where widespread dune stabilization is attributed to the sheltering effect of the urban area on surface wind velocity; and (2) the acceleration zone where airflow is deflected away from the urbanized area, causing an increase in sediment transport potential and surface erosion. Consistent coherent turbulent structures were identified at landform and dunefield scales: counter-rotating vortices develop in the lee-side flow of dune crests and shedding off the buildings on the downwind edge of the urban area. This study illustrates the direct geomorphic impact of urbanization on aeolian dunefield dynamics, a relationship that has received little previous attention. The study provides a template for investigations of the potential impact of urbanization in arid zones.

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UAV‐SfM‐based field quantification of barchan dune celerity and morphodynamics in Gonghe Basin

Shao,

Luo,

Che

et al. 2024

Earth Surf Processes Landf

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Barchan dunes do not often coexist with grasslands. However, in Gonghe Basin, north‐eastern part in Qinghai‐Tibetan Plateau (QTP), China, many barchan dunes are distributed on the grassland at high altitude. Identifying celerity and morphodynamics of barchan dunes and exploring the interaction between barchans and grassland landscape can help us better understand aeolian system sand mitigate damages. In this work, we tracked dune celerity and observed three‐dimensional changes of symmetrical and asymmetrical barchan dunes in Ertala based on high‐resolution UAV‐SfM reconstruction in short‐term monitoring and discussed the factors influencing dune celerity and deformation at high altitude. The results revealed that the barchan dunes are highly mobile with an average celerity of 0.85 m/M for the whole study area. Based on observations of dune morphology and dynamics, we found the following: (1) The dune deformation degree in a short time is not large but is widespread, especially in the elongated arm of asymmetric dune. The deformation of symmetric dune is symmetrical, whereas that of dune with extended horn is asymmetrical; (2) the sand supply, vegetation and airflow at low air density all influence the celerity and deformation degree in the development of barchan dunes; (3) the asymmetric airflow and sediment supply are important cause of dune asymmetry. The above results help us understand the deformation of barchan dune from the three‐dimensional, especially the difference reflected by the symmetry of barchan dune at high altitude.

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Three-dimensional airflow and sediment transport patterns over barchan dunes

Cited by 38 publications

References 66 publications

Morphometric analysis of slipface processes of an aeolian dune: Implications for grain‐flow dynamics

Morphometric analysis of slipface processes of an aeolian dune: Implications for grain‐flow dynamics

Quantifying the role of urbanization on airflow perturbations and dunefield evolution

UAV‐SfM‐based field quantification of barchan dune celerity and morphodynamics in Gonghe Basin

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