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Kelvin-Helmholtz instability in the presence of variable viscosity for mudflow resuspension in estuaries

Harang, Alice and Thual, Olivier and Brancher, Pierre and Bonometti, Thomas Kelvin-Helmholtz instability in the presence of variable viscosity for mudflow resuspension in estuaries. (2014) Environmental Fluid Mechanics. ISSN 1567-7419

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Official URL: http://dx.doi.org/10.1007/s10652-014-9337-4

Abstract

The temporal stability of a parallel shear flow of miscible fluid layers of dif- ferent density and viscosity is investigated through a linear stability analysis and direct numerical simulations. The geometry and rheology of this Newto- nian fluid mixing can be viewed as a simplified model of the behavior of mud- flow at the bottom of estuaries for suspension studies. In this study, focus is on the stability and transition to turbulence of an initially laminar configuration. A parametric analysis is performed by varying the values of three control pa- rameters, namely the viscosity ratio, the Richardson and Reynolds numbers, in the case of initially identical thickness of the velocity, density and viscosity profiles. The range of parameters has been chosen so as to mimic a wide variety of real configurations. This study shows that the Kelvin-Helmholtz instability is controlled by the local Reynolds and Richardson numbers of the inflection point. In addition, at moderate Reynolds number, viscosity strat- ification has a strong influence on the onset of instability, the latter being enhanced at high viscosity ratio, while at high Reynolds number, the influ- ence is less pronounced. In all cases, we show that the thickness of the mixing layer (and thus resuspension) is increased by high viscosity stratification, in particular during the non-linear development of the instability and especially pairing processes. This study suggests that mud viscosity has to be taken into account for resuspension parameterizations because of its impact on the inflec- tion point Reynolds number and the viscosity ratio, which are key parameters for shear instabilities.

Item Type:Article
Additional Information:Thanks to Springer editor. The original PDF can be found at Environmental Fluid Mechanics website: http://link.springer.com/article/10.1007%2Fs10652-014-9337-4
HAL Id:hal-00951503
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Laboratory name:
Funders:
DGA (Direction Générale de l’Armement) - CALMIP (Projet P1016) - CINES (imf6359) - IDRIS (Projet 99651)
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Deposited By: Olivier THUAL
Deposited On:24 Feb 2014 17:34

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