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Theses

Etude de quelques aspects du transport éolien des matériaux granulaires: Processus de saltation et formation des rides.

Abstract : The study of this thesis deals with the problematic of eolian sand transport. We investigate the saltation process which is the main transport mechanism of grains in an air flow. Saltating grains move typically by successive jumps over a granular bed. As these grains collide with the bed, some grains are ejected. The ejection mechanism has been studied through a model experiment of collision between an incident bead and a two-dimensional granular packing. The process has been studied, in details, varying the impact speed of the bead, the packing height, the elastic properties of the bead and the packing disorder. Distribution laws for ejection speeds have been established. Furthermore, we have shown that the ejection process is extermely sensitive to the disorder in the packing: in the case of a disordered packing, a greater number of beads are ejected. At last, we develop a phenomenological model based on a simplified description of the propagation of the shock wave in the packing.
The last part of the thesis deals with some aspects of eolian transport at another scale: the larger scale of wind ripples and sand dunes. We proposed a model for ripple formation which predicts the spatio-temporal evolution of these patterns. The parameters of the model are directly linked to the ejection laws determined experimentally. We show, in particular, that the ripples coarsen in course of time, which is experimentally observed.
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https://tel.archives-ouvertes.fr/tel-00199032
Contributor : François Rioual <>
Submitted on : Tuesday, December 18, 2007 - 12:13:19 PM
Last modification on : Friday, January 15, 2021 - 2:52:04 PM
Long-term archiving on: : Monday, April 12, 2010 - 8:19:13 AM

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  • HAL Id : tel-00199032, version 1

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François Rioual. Etude de quelques aspects du transport éolien des matériaux granulaires: Processus de saltation et formation des rides.. Physique [physics]. Université Rennes 1, 2002. Français. ⟨tel-00199032⟩

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