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Étude expérimentale d’écoulements soumis à une transition longitudinale de rugosité en lit simple et en lit composé

Abstract : This PhD thesis investigates the effect of a longitudinal change in floodplain land use on an overflooding river flow. We consider a transition between a meadow and a woodland and vice versa. This change in land use is associated with a change in hydraulic roughness, between a bed roughness (highly submerged meadow) and emergent macro-roughnesses (trees), respectively modelled by a plastic artificial grass and an array of emergent cylinders. The flows are experimentally investigated in an 18 m x 3 m laboratory flume. In a first step, we investigate the flow through a cylinder array in a single channel, focusing on the effect of bed roughness on the cylinder wakes and on the seiche phenomenon (strong free surface oscillations). In a second step, we study the development towards flow uniformity of compound channel flows with a uniform hydraulic roughness on the floodplains. The asymmetrical growth of the compound channel mixing layer, the self-similarity property and the three-dimensional organisation of the turbulent coherent structures associated with the mixing layer are analysed. In a third step, we investigate the longitudinal change in roughness in compound channel configuration, which effects on mixing layer and on coherent structures are discussed. We also assess the contributions to lateral transfers of momentum between main channel and floodplain by turbulent diffusion, by mass exchange and by secondary currents
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Submitted on : Tuesday, December 6, 2016 - 11:09:06 AM
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  • HAL Id : tel-01409745, version 1
  • IRSTEA : PUB00051102

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Victor Dupuis. Étude expérimentale d’écoulements soumis à une transition longitudinale de rugosité en lit simple et en lit composé. Mécanique des fluides [physics.class-ph]. Université de Lyon, 2016. Français. ⟨NNT : 2016LYSE1154⟩. ⟨tel-01409745⟩

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