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Ecoulements à surface libre de fluides à seuil : rhéométrie et validation des caractéristiques hydrauliques dans un canal à fond mobile. Application aux laves torrentielles

Abstract : This thesis presents an experimental study dedicated to characterise the hydraulic propertiesof free surface flows of complex fluids : viscoplastic fluids and mixtures made of viscoplasticfluids and grains. This study is motivated by the need to improve knowledge on properties ofthe flow of debris flows in a context of protection against natural hazards in the mountains.We have developed an original laboratory device - a channel with a mobile bottom - togenerate gravitary flows that are globally stationary in the laboratory frame. The flows have avery steep front followed upstream by a zone of uniform thickness. Viscoplastic fluids used(carbopol and kaolin) were selected so to model the matrix of natural mud flows, taking intoaccount the criteria of similarity adapted. These fluids follow a behavior law of Herschel-Bulkley, and their rheological properties were determined using a laboratory rheometer byproviding a particular care to the establishment of the associated uncertainties. We presentaccurate measurements of the evolution of the thickness of the flow in the uniform zone withthe the velocity speed of channel belt. These results are compared with theoretical predictionscorresponding to a steady uniform flow of a fluid of Herschel-Bulkley, and we show that theagreement is satisfactory through the uncertainties on the rheological measurements. We alsoanalyzed the shape of front, and here too, the agreement with hydraulic models (models likeSaint-Venant) is good. Both of the studies allowed to validate the hydraulic predictionsobtained from behavior laws measured with the rheometer. Finally, in a last section, wepresent a Preliminary study about the dynamics of isolated rigid particles placed in the flow,by paying attention to longitudinal velocities and falling velocities for different particle sizesand densities.
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Submitted on : Monday, July 30, 2012 - 11:08:13 AM
Last modification on : Friday, March 25, 2022 - 9:41:12 AM
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Assia Ghemmour. Ecoulements à surface libre de fluides à seuil : rhéométrie et validation des caractéristiques hydrauliques dans un canal à fond mobile. Application aux laves torrentielles. Autre. Université de Grenoble, 2011. Français. ⟨NNT : 2011GRENI060⟩. ⟨tel-00721734⟩

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