Flow dynamics over a foredune scarp

Piscioneri, Ned; Smyth, Thomas; Hesp, Patrick A.

doi:10.1002/esp.4555

Cited by 29 publications

(33 citation statements)

References 62 publications

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“…To capture the turbulent nature of wind flow around the walls, flares loaded with theatrical smoke were deployed upwind of the test walls when the prevailing wind was perpendicular to the test wall (Piscioneri et al ., 2019). The flares lasted approximately 3 min.…”

Section: Data Collectionmentioning

confidence: 99%

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Modelling the risk of deterioration at earthen heritage sites in drylands

Richards

Mayaud

Zhan

et al. 2020

Earth Surf Processes Landf

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The variable climatic and environmental conditions associated with dryland regions can cause rapid erosion to both natural and man‐made earthen structures. Whilst there is a long history of research into the evolution of erosional landforms such as yardangs, little research has investigated how dryland processes influence the erosion of built structures. Earthen heritage sites located in arid and semi‐arid environments experience rapid deterioration caused by exposure to environmental drivers such as wind and rain. Understanding how these environmental drivers interact with each other and cause deterioration to earthen material is vital for successful conservation strategies. To address this need, we present the Vegetation and Sediment TrAnsport model for Heritage Deterioration (ViSTA‐HD) that simulates the risk of polishing, pitting and slurry on earthen heritage in a spatially specific manner. A technical description of the model is provided, and sensitivity and validation tests are reported. The model is then used to simulate the risk of deterioration occurring over centennial timescales at a Suoyang Ancient City, located in semi‐arid northwest China. The modelled risk of deterioration is in good agreement with deterioration patterns found at Suoyang, with the risk of polishing predominantly occurring around the wall edges, areas at risk of pitting echoing the dune formation and the risk of slurry occurring in drape‐like patterns down the wall face. Consequently, ViSTA‐HD is a powerful and versatile model that can be used to help inform our understandings of long‐term interactions between dryland processes and deteriorative impact on earthen structures. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd

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Section: Data Collectionmentioning

confidence: 99%

“…The flares lasted approximately 3 min. Smoke flow was video‐recorded, and stills from the videos used to capture turbulent flow patterns in front and around the wall face (Livingstone, 1986; Piscioneri et al ., 2019). Macro‐scale smoke patterns were used to visualize sediment transport pathways around the walls.…”

Section: Data Collectionmentioning

confidence: 99%

Modelling the risk of deterioration at earthen heritage sites in drylands

Richards

Mayaud

Zhan

et al. 2020

Earth Surf Processes Landf

View full text Add to dashboard Cite

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“…For instance, during post‐storm recovery scarps fill up by wind‐blown sand deposited at the dune foot, building a so‐called dune ramp (e.g., Carter et al., 1990, Ollerhead et al., 2013), altering sediment transport and deposition patterns across the foredune. Previous studies used numerical models to compare flow deflection across a scarped and nonscarped foredune, with uncertain implications on dune recovery (Hesp & Smyth, 2016a, 2019; Piscioneri et al., 2019). Volumetric field observations led to conceptual insights, showing that a dune ramp has a major impact on sand transported to the dune crest and lee slope, where scarped dunes devoid of a dune ramp show significantly reduced crest directed transport (Castelle et al., 2017; Christiansen & Davidson‐Arnott, 2004; Donker et al., 2018; Ollerhead et al., 2013; Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Wind and Sand Transport Across a Vegetated Foredune Slope

et al. 2021

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Vegetated foredunes are widespread aeolian landforms along wave‐dominated sandy coasts. In contrast to previous advances in dune erosion during storm surges, there is a little empirical data and understanding of aeolian processes during foredune recovery and growth. Based on a comprehensive data set (airflow, sand transport, topography change, and vegetation cover) collected across a steep (1:2.5, 21.8°), high (20 m) foredune during a windy 5‐week period at Egmond aan Zee, the Netherlands, we demonstrate in agreement with previous studies that shore‐perpendicular winds accelerate by a factor of 3 from dune foot to crest but result in low aeolian mass fluxes that are maximum at the dunefoot, favoring local deposition. In contrast, oblique and alongshore winds up the foredune are accelerated less (or even decelerate) but are important in bringing sand from the dunefoot on to the foredune slope, where it is deposited when vegetation cover exceeds about 50% of the maximum density measured on the dune crest. Moreover, our data suggest that sediment flux at the dune foot is limited by fetch‐induced sediment availability, whereas sediment flux at the dune crest is limited by transport capacity, which depends on the wind velocity and the distance traveled over vegetation. Our study thus highlights the importance of wind direction and vegetation cover to foredune growth and recovery.

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“…Scarping or cliffing of coastal dunes, and particularly foredunes, is very common. Scarping is usually caused by wave action during high tides, storms, and/or storm surge (Carter and Stone, 1989;Carter et al, 1990;Hesp, 2002;Jarmalavicius et al, 2012;Karunarathna et al, 2018;Piscioneri et al, 2019). It may also occur as a result of stream action where, for example, streams migrate alongshore, or breakout from a landward dune area as washouts (Calliari;1998;.…”

Section: Introductionmentioning

confidence: 99%

CFD flow dynamics over model scarps and slopes

Hesp

Smyth

2019

Physical Geography

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As sea level rises, and during storm and surge events, coastal dunes may become cliffed or scarped by wave action. Knowledge of wind flow over dune scarps, and as scarps fill, their subsequent various slopes, is an essential first step to understanding sediment transport pathways from the beach to the dunes. In this study, flow over scarps (also termed forward facing steps) is reviewed, and the flow over a vertical scarp (90°) and three slopes of 45°, 24° and 14°, all 2 m in height, is examined via CFD modelling. The flow over three 90° scarps with heights of 1 m, 2 m and 4 m, and over a 2 m high vertical (90°) scarp for three increasingly oblique incident winds is also studied. The extent of wind flow deceleration, separation and recirculation becomes smaller with decreased slope, with maximum flow separation and reverse vortex development occurring in the front of the vertical scarp. The extent of crest wind flow separation and recirculation is greatest for the scarp (7.8 m in length), and is considerably less for the 45° slope (2.4 m in length). As scarp height increases, so too does the spatial extent of turbulent wind flow, wind speed, and extent of the flow separation region. For cases where the scarp slope varied but height remained constant, the extent of the flow separation region was greatest when the scarp was vertical. Wind flow separation was dramatically reduced below a scarp slope of 45°. As incident wind direction became more oblique over a vertical scarp, wind speed undergoes significantly less deceleration, and helicoidal vortices replace roller vortices. Our results demonstrate how scarp morphology and wind direction are likely to influence transport pathways.

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Flow dynamics over a foredune scarp

Cited by 29 publications

References 62 publications

Modelling the risk of deterioration at earthen heritage sites in drylands

Modelling the risk of deterioration at earthen heritage sites in drylands

Wind and Sand Transport Across a Vegetated Foredune Slope

CFD flow dynamics over model scarps and slopes

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