Stability of bedforms in laminar flows with free surface: from bars to ripples | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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  Stability of bedforms in laminar flows with free surface: from bars to ripples

Type de publication:

Journal Article

Source:

Journal of Fluid Mechanics, Volume 642, p.329-348 (2010)

ISBN:

0022-1120

Numéro d'accès:

ISI:000274490500015

URL:

http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=6902044

Mots-clés:

UMR 7154 ; Dynamique des Fluides Géologiques ; absolute/convective; lubrication theory/thin films; sediment transport

Résumé:

<p>The present paper is devoted to the formation of sand patterns by laminar flows. It focuses on the rhomboid beach pattern, formed during the backswash. A recent bedload transport model, based on a moving-grains balance, is generalized in three dimensions for viscous flows. The water flow is modelled by the full incompressible Navier-Stokes equations with a free surface. A linear stability analysis then shows the simultaneous existence of two distinct instabilities, namely ripples and bars. The comparison of the bar instability characteristics with laboratory rhomboid patterns indicates that the latter could result from the nonlinear evolution Of unstable bars. This result, together with the sensibility of the stability analysis with respect to the parameters of the transport law, suggests that the rhombold pattern could help improving sediment transport models, so critical to geomorphologists.</p>

Notes:

Devauchelle, O. Malverti, L. Lajeunesse, E. Lagree, P. -Y. Josserand, C. Thu-Lam, K. -D. Nguyen