Étude des rides sédimentaires générées par les vagues sur le plateau continental

Marieu, Vincent; Bonneton, Philippe; Ardhuin, Fabrice; Foster, D. L.; Oh, Columbus

doi:10.5150/jngcgc.2006.026-m

Cited by 2 publications

(2 citation statements)

References 6 publications

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“…As chapter 3 shows, the use of this sediment transport formulation, particularly in case (S1a), lead to numerical instabilities. Two reasons may explain this shortcoming: first, the effect of diffusivity in the bedslope contribution could be underestimated, second, the discretization method applied to the sediment conservation equation could be inadequate, a more sophisticated numerical scheme such as a non-oscillatory scheme could be necessary (Saint-Cast, 2002;Marieu et al, 2006).…”

Section: • (S1)mentioning

confidence: 99%

“…The second option is to adapt this formulation to the Soulsby and Van Rijn formula and a third is to implement a quasi three dimensional formulation, by considering a vertical (non averaged) distribution of the current. By using a more realistic sediment transport formulation, a more sophisticated numerical scheme such as a non-oscillatory scheme (Saint-Cast, 2002;Marieu et al, 2006) could be necessary for the discretization of the sediment conservation equation.…”

Section: Model Improvementmentioning

confidence: 99%

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Nonlinear Modelling of surf zone morphodynamical instabilities

Garnier

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Esta tesis se dedica en un estudio de estabilidad no lineal de la morfodinàmica de la zona de rompientes de playas de arena. El modelo numérico MORFO55 resuelve las ecuaciones de aguas someras no lineales para la hidrodinámica y actualiza la topografía a partir del transporte de sedimento. En primer lugar, se aplica en el caso de playas complejas longitudinalmente no uniformes con objeto de probar sus distintas formulaciones. En secundo lugar, se usa para estudiar la generación de estructuras rítmicas en playas longitudinalmente uniformes. Entre estos patrones se distinguen las barras transversales y oblicuas, las barras crescenticas y los sistemas de barras/surcos (ridges/runnels). La hipótesis de que emergen a partir de inestabilidades internas del acoplamiento entre la topografía y la hidrodinámica se investiga. Los estudios previos de modelización numérica se limitaban a las etapas iniciales de la generación de las barras. En particular, mostraban que las barras transversales y oblicuas pueden formarse en playas planas mientras que las barras crecenticas aparecen en playas con barra. La formación de los sistemas de barras/surcos se explica con modelos conceptuales de la observación mediante satélite según los cuales emergerán a partir de la deformación de la barra intermareal. Esta tesis estudia el régimen no lineal de la evolución de todos estos sistemas. Particularmente se obtiene un estado 'nal de equilibrio. Los resultados generales coinciden cualitativamente con las barras observadas en la naturaleza. Se da una interpretación física de la formación, de la evolución y de la saturación del crecimiento de las barras. This thesis performs a nonlinear stability study of the surf zone morphodynamics of sandy beaches. To this end the MORFO55 model based on a wave and depth averaged nonlinear shallow water equations solver with wave driver, sediment transport and bed updating is presented. It is first applied to complex longitudinally non-uniform beaches in order to test different model formulations. Second, it is applied to study the generation of surf zone rhythmic features on alongshore uniform beaches. Shore-attached transverse or oblique bars, crescentic bars and ridge and runnel systems are well known examples of such features. The hypothesis that they emerge by self organisation of the coupling between topography, waves and currents is here tested. In absence of shore-parallel bars, the initial formation of transverse and oblique bars had been shown by previous modelling studies of linear stability analysis but is now extended to the finite amplitude regime. In most of barred beaches, crescentic bars and ridge and runnel systems appear. Conceptual models based on field observations suggest that ridges and runnels could emerge by the deformation of the alongshore intertidal bar intercepted by crescentic bars. Up to now, only the formation of crescentic bars had numerically succeeded with linear and non linear models. This study shows that a dynamical equilibrium state of each of these rhythmic bar systems may be described with a numerical model. General results are in qualitative agreement with the bar systems observed in nature. A physical explanation for their formation, their evolution and the saturation of their growth is given.

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Section: • (S1)mentioning

confidence: 99%

Section: Model Improvementmentioning

confidence: 99%

Nonlinear Modelling of surf zone morphodynamical instabilities

Garnier

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Modeling of vortex ripple morphodynamics

Marieu¹,

Bonneton²,

Foster³

et al. 2008

J. Geophys. Res.

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[1] A new morphology module has been developed in order to perform simulations of the bed form evolution under hydrodynamic forcing. This module has been implemented into the numerical model Dune2D, which solves the Reynolds Averaged Navier-Stokes (RANS) equations in the boundary layer and resolves sediment transport over moving sand beds. The morphology module is composed of a modified central scheme and a routine that simulates avalanches and has been successfully applied to the study of orbital ripples evolution. Ripple growth from a quasiflat bed have been simulated, and the growth behavior has been compared to previous experimental measurements. The simulated ripples reach an equilibrium state where energy damping processes (avalanches) compensate energy production processes (flux of sediment). These processes have been analyzed during ripple creation, growth, merging, and annihilation. Furthermore, sandy bed evolutions have been simulated with random initial bed forms in order to examine the influence of the bed ''history'' on the final solution and the wave energy dissipated during these evolutions.

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Étude des rides sédimentaires générées par les vagues sur le plateau continental

Cited by 2 publications

References 6 publications

Nonlinear Modelling of surf zone morphodynamical instabilities

Nonlinear Modelling of surf zone morphodynamical instabilities

Modeling of vortex ripple morphodynamics

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