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Contribution à la modélisation de l'érosion de fortes pentes par un écoulement turbulent diphasique

Abstract : To better understand the basic phenomena involved in hydraulic erosion, the influence of the eroded mass flow rate on the velocity field of the water flow is investigated by an original theoretical model. Here we simply consider the situation of a turbulent two-phase flow over a non-deformable solid medium with both turbulent stresses and turbulent particles diffusion in the flow. In the reference frame linked to the ground surface, the flow can be considered as a quasi-steady state and modelled by the well known boundary layer equations. The dynamic equations and the mass conservation equations are solved simultaneously. The Rankine-Hugoniot equations are used to describe the boundary jump conditions at the interface between the fluid and the ground, and a law of erosion is fixed to evaluate the local mass flow of eroded materials. As we consider here a purely mechanical erosion process, we can reasonably postulate a threshold law: the eroded mass flow rate is simply proportional to the difference between the tangential stress induced by the flow and a critical value characteristic of the soil. In this theoretical frame, we can study the influence of several parameters, as the sediments density or the ground slope, for two different configurations, namely a boundary layer and a free surface flow. A differential law of turbulent diffusion is also proposed taking into account the vertical pressure gradient within the flow. A strong coupling between the fluid flow, the erosion process and the eroded suspended matter is clearly underlined. In particular, for a boundary layer flow, the existence of a critical ground slope is found, above which the presence of the already eroded sediments amplifies the erosion that becomes unlimited downstream. This modelling proposes an original description of the phenomenon of local erosion. To become a practical and simple tool, it should be confronted with experimental results and validated.
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https://tel.archives-ouvertes.fr/tel-00010479
Contributor : Olivier Brivois <>
Submitted on : Friday, October 7, 2005 - 2:39:48 PM
Last modification on : Thursday, January 23, 2020 - 6:22:03 PM
Long-term archiving on: : Friday, April 2, 2010 - 10:36:15 PM

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  • HAL Id : tel-00010479, version 1

Citation

Olivier Brivois. Contribution à la modélisation de l'érosion de fortes pentes par un écoulement turbulent diphasique. Mécanique [physics.med-ph]. Université de la Méditerranée - Aix-Marseille II, 2005. Français. ⟨tel-00010479⟩

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