Reversing transverse dunes: Modelling of airflow switching using 3D computational fluid dynamics

Jackson, Derek W.T.; Cooper, J. Andrew G.; Green, Andrew N.; Beyers, Meiring; Guisado‐Pintado, Emilia; Wiles, Errol; Benallack, Keegan; Balme, M. R.

doi:10.1016/j.epsl.2020.116363

Cited by 21 publications

(24 citation statements)

References 36 publications

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“…reversing dune (Jackson et al, 2020). Furthermore, the eroded sands near the dune crest are transported and then deposited at the top of stoss side, where they form a reversing slip face due to sand avalanching.…”

Section: Alternating Winds and Sedimentary Characteristicsmentioning

confidence: 99%

“…When airflow reverses on barchanoid dunes, their crests move by reworking the lee side and generating a new slip face on stoss side. They then eventually reform into reversing barchanoid dunes (Gao et al., 2021; Jackson et al., 2020). Reversing dunes have been reported in various environments on Earth and other planets where dunes are shaped under the combined effect of two dominant winds responsible for frequent crest reversals (Bristow et al., 2010; Gao et al., 2021; Jackson et al., 2020; Neuman et al., 1997; Walker, 1999).…”

Section: Introductionmentioning

confidence: 99%

“…Positive feedback between topography and near‐surface airflow leads to different degrees of wind erosion and deposition at various dune positions. These are reflected in the grain size compositions of the aeolian sands and cause different GSD patterns (Gao, Narteau, & Rozier, 2015; Jackson et al., 2020; Qian et al., 2009; Visher, 1969). Therefore, analysis of grain‐size parameters is the basis for determining the process‐response characteristics of individual sediment units and their environments (Yang et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

“…They then eventually reform into reversing barchanoid dunes (Gao et al., 2021; Jackson et al., 2020). Reversing dunes have been reported in various environments on Earth and other planets where dunes are shaped under the combined effect of two dominant winds responsible for frequent crest reversals (Bristow et al., 2010; Gao et al., 2021; Jackson et al., 2020; Neuman et al., 1997; Walker, 1999). Previous studies have investigated changes in surface airflow, sand flux, and surface sand grain‐size characteristics among reversing dunes (Jackson et al., 2020; Lancaster et al., 2002; Neuman et al., 1997).…”

Section: Introductionmentioning

confidence: 99%

“…among reversing dunes (Jackson et al, 2020;Lancaster et al, 2002;Neuman et al, 1997). The morphodynamics of reversing dunes have also been studied (Dong et al, 2011;Gao et al, 2021).…”

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confidence: 99%

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The Effects of Seasonal Wind Regimes on the Evolution of Reversing Barchanoid Dunes

et al. 2022

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Transitions in dune morphology reflect the complex effects of wind regimes and ground surface characteristics (e.g., dune morphology, vegetation cover, and moisture content) on aeolian transport dynamics (Lancaster, 1995;Wang et al., 2002;Yang et al., 2021;Zhang et al., 2020). Under a unidirectional wind regime, barchanoid and transverse dunes could be developed depending on the variation of sand availability. Longitudinal or oblique dunes are commonly found under bidirectional wind regimes (Rubin & Hunter, 1987). Under the influence of the East Asian monsoon system, near-surface wind strengths and directions are characterized by strong northwest winds in spring and winter, and weak southeast winds in summer. Notably, the seasonal alternation of wind regimes characterized by two winds that blow from opposite directions usually causes reversing dunes to form (McKee, 1979). When airflow reverses on barchanoid dunes, their crests move by reworking the lee side and generating a new slip face on stoss side. They then eventually reform into reversing barchanoid dunes (Gao et al., 2021;Jackson et al., 2020). Reversing dunes have been reported in various environments on Earth and other planets where dunes are shaped under the combined effect of two dominant winds responsible for frequent crest reversals (

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Section: Alternating Winds and Sedimentary Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…among reversing dunes (Jackson et al, 2020;Lancaster et al, 2002;Neuman et al, 1997). The morphodynamics of reversing dunes have also been studied (Dong et al, 2011;Gao et al, 2021).…”

mentioning

confidence: 99%

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The Effects of Seasonal Wind Regimes on the Evolution of Reversing Barchanoid Dunes

et al. 2022

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Wind flow dynamics and sand deposition behind excavated foredune notches on developed coasts

Nguyen

Hilton

Wakes

2022

Earth Surf Processes Landf

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This study examines wind flow dynamics and downwind sand deposition behind engineered notches in a foredune system on a developed coast. Recent studies have examined the morphodynamics downwind of such notches, however, wind flow dynamics and sand deposition in the lee of such notches is not well understood, particularly in relation to artificial foredunes on developed coasts. Wind flow dynamics behind an excavated notch at St Kilda beach, Dunedin, New Zealand is measured using vertical arrays of ultrasonic anemometers. Field data is used to validate computational fluid dynamic flow simulations to examine flow dynamics behind a foredune section with multiple notches. Sand deposition behind the notches is measured using sand pot traps. Wind direction across the depositional lobe aligns with notch orientation and the normalized wind speed increases when the incident wind direction is >10° to the shoreline in a notch that orientates 67° to the shoreline. Wind speed in the swale downwind a notch decreases when the incident wind direction shifts from alongshore to onshore normal. Flow reversal occurs when the incident wind direction approaches onshore normal (>72° to the shoreline). Helicoidal flow appears to occur in the lee of the higher foredune section when the incident wind direction is 74° to the shoreline, while alongshore flow dominates in the lower section. Most sand deposition occurs within 5 m of the depositional lobe of the notch. The orientation of excavated notches should be less than 74° relative to the shoreline to prevent the occurrence of flow reversal in the swale, which might reduce the distance that sand can be transported inland from the notches when the incident wind direction is parallel to the notch axis.

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CFD simulations of wind flow across scarped foredunes: Implications for sediment pathways and beach–dune recovery after storms

Bauer

Wakes

2022

Earth Surf Processes Landf

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Beach–dune systems are dynamic geomorphic environments subject to erosion during storms and reconstruction during swell‐dominated inter‐storm periods. Wave‐cut scarps are frequently carved into the beach–dune profile, occasionally eroding the stoss slope of the foredune. Although the rapid phases of erosion have been researched and modelled extensively, relatively little is known about beach–dune recovery, especially scarp healing by aeolian processes. Computational fluid dynamic (CFD) modelling was deployed in this study to yield insights into different flow patterns across beach–dune profiles with three model foredunes (unscarped, 1 m scarp, 2 m scarp) for varying wind approach angles (α = 0–45°). The results show that the presence of a scarp substantially modifies the flow dynamics on the backbeach in front of the foredune. Vertical profiles of turbulence kinetic energy indicate that the influence of this flow‐modified zone extends out to about −7h from the scarp base (where h is the scarp height). The reduction in onshore wind speed that is characteristic of this flow‐modified zone favours sand deposition on the backbeach and sand ramp development at the base of the scarp. Shore‐normal wind approach angles yield discontinuous roller‐like vortices with reversing (offshore) flow components at the sand surface, accompanied by the evolution of echo dunes. Oblique wind approach angles yield corkscrew (helicoidal) vortices that lead to the formation of continuous sand ramps alongshore. A conceptual model of scarp healing based on ideas previously discussed in the literature and enhanced by the CFD simulation results highlights the importance of sand ramps for reconnecting the transport system on the beach to the foredune stoss slope, thereby facilitating foredune growth and maintenance.

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Reversing transverse dunes: Modelling of airflow switching using 3D computational fluid dynamics

Cited by 21 publications

References 36 publications

The Effects of Seasonal Wind Regimes on the Evolution of Reversing Barchanoid Dunes

The Effects of Seasonal Wind Regimes on the Evolution of Reversing Barchanoid Dunes

Wind flow dynamics and sand deposition behind excavated foredune notches on developed coasts

CFD simulations of wind flow across scarped foredunes: Implications for sediment pathways and beach–dune recovery after storms

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