Secondary flow deflection in the lee of transverse dunes with implications for dune morphodynamics and migration

• Published in: Earth surface processes and landforms Vol. 38; no. 14; pp. 1642 - 1654
• Main Authors: Walker, Ian J., Shugar, Dan H.
• Format: Journal Article
• Language: English
• Published: Chichester Blackwell Publishing Ltd 01.11.2013; Wiley; Wiley Subscription Services, Inc
• Subjects: aeolian dunes; Airflow; Arrays; Bgi / Prodig; Deflection; Dunes; flow reversal; flow separation; Geomorphology; interdune; lee-side; Methods and techniques; Migration; Physical geography; Sand; Three dimensional; Transport; Atmospheric circulation; Aeolian features; Wind; Sand; Ground survey; Dune; Model; Earth surface processes; Aeolian transport
• ISSN: 0197-9337; 1096-9837
• DOI: 10.1002/esp.3398

ABSTRACT Measurements of lee‐side airflow response from an extensive array of meteorological instruments combined with smoke and flow streamer visualization is used to examine the development and morphodynamic significance of the lee‐side separation vortex over closely spaced transverse dune ridges. A differential deflection mechanism is presented that explains the three‐dimensional pattern of lee‐side airflow structure for a variety of incident flow angles. These flow patterns produce reversed, along‐dune, and deflected surface flow vectors in the lee that are inferred to result in net ‘lateral diversion’ of sand transport over one dune wavelength for incident angles as small as 10° from crest‐transverse (i.e. 80° from the crest line). This lateral displacement increases markedly with incident flow angle when expressed as the absolute value of the total deflection in degrees. Reversed and multi‐directional flow occurs for incident angles between 90° and 50°. These results document the three‐dimensional nature of flow and sand transport over transverse dunes and provide empirical evidence for an oblique migration model. Copyright © 2013 John Wiley & Sons, Ltd.