Computational Fluid Dynamic modelling of Three-Dimensional airflow over dune blowouts

Thomas Smyth, Derek Jackson, Andrew Cooper

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Blowout enlargement is primarily driven by aeolian transport, where high velocity winds entrain and remove sediment from the landform. However patterns of deflation in blowouts are poorly understood as near surface airflow in a blowout is complex. In this study three-dimensional airflow during a light (3.93 m/s) and moderate (8.98 m/s) onshore wind event was calculated using the two-equation Renormalized Group k-epilson airflow turbulence model, by the Computational Fluid Dynamics software OpenFOAM. The saucer blowout located on the coastal foredune in the Belmullet Peninsula, Western Ireland, measures 100 metres long, 60 metres wide and 13 metres deep. Results show that during both wind events flow separates and reverses as it enters the blowout over the foredune crest, as it reattaches it is steered, diverging from the centre of the blowout and before
topographically accelerating over the rim crest. Flow which enters the throat of the blowout accelerates and remains directionally unchanged before accelerating up the deposition lobe slope, where flow at the crest was simulated as being 100% faster at the crest than velocity simulated on the beach. In lee of the blowout at the depositional lobe airflow decelerated and a large zone of flow separation and reversal was created. Whilst relative change of velocity and direction at 1 metre above the surface of the blowout displayed similar behaviour during both wind events, flow in the lee during the light wind event did not appear to fully reattach and recover to velocity levels on the beach.
LanguageEnglish
Pages314-318
Number of pages5
JournalJournal of Coastal Research
Issue numberSI 64
Publication statusPublished - 2011
Externally publishedYes

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blowout
computational fluid dynamics
airflow
dune
modeling
beach
deflation
landform
wind velocity
turbulence
software

Cite this

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title = "Computational Fluid Dynamic modelling of Three-Dimensional airflow over dune blowouts",
abstract = "Blowout enlargement is primarily driven by aeolian transport, where high velocity winds entrain and remove sediment from the landform. However patterns of deflation in blowouts are poorly understood as near surface airflow in a blowout is complex. In this study three-dimensional airflow during a light (3.93 m/s) and moderate (8.98 m/s) onshore wind event was calculated using the two-equation Renormalized Group k-epilson airflow turbulence model, by the Computational Fluid Dynamics software OpenFOAM. The saucer blowout located on the coastal foredune in the Belmullet Peninsula, Western Ireland, measures 100 metres long, 60 metres wide and 13 metres deep. Results show that during both wind events flow separates and reverses as it enters the blowout over the foredune crest, as it reattaches it is steered, diverging from the centre of the blowout and beforetopographically accelerating over the rim crest. Flow which enters the throat of the blowout accelerates and remains directionally unchanged before accelerating up the deposition lobe slope, where flow at the crest was simulated as being 100{\%} faster at the crest than velocity simulated on the beach. In lee of the blowout at the depositional lobe airflow decelerated and a large zone of flow separation and reversal was created. Whilst relative change of velocity and direction at 1 metre above the surface of the blowout displayed similar behaviour during both wind events, flow in the lee during the light wind event did not appear to fully reattach and recover to velocity levels on the beach.",
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Computational Fluid Dynamic modelling of Three-Dimensional airflow over dune blowouts. / Smyth, Thomas; Jackson, Derek ; Cooper, Andrew.

In: Journal of Coastal Research, No. SI 64, 2011, p. 314-318.

Research output: Contribution to journalArticle

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AU - Jackson, Derek

AU - Cooper, Andrew

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AB - Blowout enlargement is primarily driven by aeolian transport, where high velocity winds entrain and remove sediment from the landform. However patterns of deflation in blowouts are poorly understood as near surface airflow in a blowout is complex. In this study three-dimensional airflow during a light (3.93 m/s) and moderate (8.98 m/s) onshore wind event was calculated using the two-equation Renormalized Group k-epilson airflow turbulence model, by the Computational Fluid Dynamics software OpenFOAM. The saucer blowout located on the coastal foredune in the Belmullet Peninsula, Western Ireland, measures 100 metres long, 60 metres wide and 13 metres deep. Results show that during both wind events flow separates and reverses as it enters the blowout over the foredune crest, as it reattaches it is steered, diverging from the centre of the blowout and beforetopographically accelerating over the rim crest. Flow which enters the throat of the blowout accelerates and remains directionally unchanged before accelerating up the deposition lobe slope, where flow at the crest was simulated as being 100% faster at the crest than velocity simulated on the beach. In lee of the blowout at the depositional lobe airflow decelerated and a large zone of flow separation and reversal was created. Whilst relative change of velocity and direction at 1 metre above the surface of the blowout displayed similar behaviour during both wind events, flow in the lee during the light wind event did not appear to fully reattach and recover to velocity levels on the beach.

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