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Interaction Surface-Atmosphère en Planétologie Comparée : Application à la formation des dunes.

Abstract : In this manuscript, we look at the interaction between surface and atmosphere. More specifically, we deal with the formation of dunes in the Solar System. We use laboratory experiments to produce downsized dunes under controlled conditions and a numerical model completes this experimental approach. These tools allow the study the formation of dunes and to follow their evolution. We highlight the formation of transverse dune fields and longitudinal dune fields under symmetrical bimodal wind regimes respectively for small and large angular separation between the two directions of wind. The transition between these two kinds of bedform occurs around an angle of 90° but is shown to depend on the wind regime period. For short period, in comparison to the time-scale of the adaptation of the dunes to instantaneous wind, the transition is shifted towards the small angular separations. This behavior goes with a more efficient coarsening of the longitudinal dunes fields. This study is followed by a work on solitary structures which emphasizes the difference of long-term stability of transverse and longitudinal dunes. When the latter remain stable, the former are instable and break into barchans (or barchanoids) when the sand supply, or the quantity of sand available, is too low. Under these bimodal wind regimes, the evolution of a sand pile leads to a great variety of morphologies. Barchanoids which shape depends on the angle between the two winds are formed for small angular separation. For an angle of 90° ̊a "chestnut"-like dune is sculpted and a longitudinal extension develops for larger angular separations. The growth of this solitary longitudinal dune reemphasizes that the longitudinal morphology is an attractor in its domain of formation. Finally, our results are compared with dune observations and used to constrain wind regimes globally on Titan and locally on Mars.
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Contributor : Erwan Reffet <>
Submitted on : Wednesday, January 4, 2012 - 10:03:57 AM
Last modification on : Monday, December 14, 2020 - 9:51:24 AM
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  • HAL Id : tel-00656378, version 1

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Erwan Reffet. Interaction Surface-Atmosphère en Planétologie Comparée : Application à la formation des dunes.. Planétologie et astrophysique de la terre [astro-ph.EP]. Université Paris-Diderot - Paris VII, 2010. Français. ⟨tel-00656378⟩

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