Flow deflection over a foredune

Hesp, P.A. and Smyth, T.A.G. and Nielsen, P and Walker, I.J. and Bauer, B.O. and Davidson-Arnott, R.G.D. (2014) Flow deflection over a foredune. Geomorphology, 230 (SI 75). pp. 64-74. ISSN 0169-555X

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Abstract

Flow deflection of surface winds is common across coastal foredunes and blowouts. Incident winds approaching obliquely to the dune toe and crestline tend to be deflected towards a more crest-normal orientation across the stoss slope of the foredune. This paper examines field measurements for obliquely incidentwinds, and compares them to computational fluid dynamics (CFD)modelling of flow deflection in 10° increments fromonshore (0°) to alongshore (90°) wind approach angles. The mechanics of flow deflection are discussed, followed by a comparative analysis of measured and modelled flow deflection data that shows strong agreement. CFD modelling of the full range of onshore to alongshore incidentwinds reveals that deflection of the incident wind flowis minimal at 0° and gradually increases as the incidentwind turns towards 30° to the dune crest. The greatest deflection occurs between 30° and 70° incident to the dune crest. The degree of flow deflection depends secondarily on height above the dune surface, with the greatest effect near the surface and toward the dune crest. Topographically forced flow acceleration (“speed-up”) across the stoss slope of the foredune is greatest for winds less than 30° (i.e., roughly perpendicular) and declines significantly for winds with more oblique approach angles. There is less lateral uniformity in the wind field when the incident wind approaches from N60° because the effect of aspect ratio on topographic forcing and streamline convergence is less pronounced.

Item Type: Article
Additional Information and Comments: NOTICE: this is the author’s version of a work that was accepted for publication in Geomorphology. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Geomorphology, Vol 230, (Feb 2015) https://doi.org/10.1016/j.geomorph.2014.11.005
Faculty / Department: Faculty of Science > Geography and Environmental Science
Depositing User: Thomas Smyth
Date Deposited: 12 Jun 2018 13:42
Last Modified: 12 Jun 2018 13:42
URI: http://hira.hope.ac.uk/id/eprint/2531

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