Modeling of vortex ripple morphodynamics

Abstract

[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.

Process-based modeling of cross-shore sandbar behavior

“…using the modified non-oscillatory central scheme of Marieu et al (2008) to prevent from spurious bed form oscillations when there are steep peaks in the sediment transport rate.…”

Modélisation de l’évolution morphodynamique des dunes sous-marines

“…Le modèle assure notamment une bonne description de la zone de recirculation (ANDERSEN, 1999). Le calcul de l'énergie cinétique turbulente k et du taux de dissipation par la turbulence  permet de déterminer la viscosité turbulente, 2.3 Module morphologique L'évolution du fond est déterminée à partir de l'équation de conservation du sédiment, résolue par un schéma centré non oscillant (NOCS) auquel est ajouté un module d'avalanche (MARIEU et al, 2008). Le schéma NOCS permet notamment de bien gérer les sauts de flux au niveau des crêtes des formes sableuses.…”

Coupling mechanisms in double sandbar systems. Part 1: patterns and physical explanation

“…Nearshore patterns along sandy wave-dominated beaches cover a wide and intriguing variety of temporal and spatial variability: ripples (Traykovski et al, 1999;Marieu et al, 2008) and megaripples (Clarke and Wermer, 2004;Gallagher et al, 1998), shoreline undulations ranging from a few (beach cusps, Guza and Inman, 1975;Coco et al, 1999) to hundreds (megacusps, Short, 1999) and thousands (coastline features such as cuspate patterns, Ashton et al, 2001;Ruessink and Jeuken, 2002) of metres and three-dimensional (3D, Short, 1999;Van Enckevort et al, 2004) or alongshore-uniform (Greenwood and Davidson-Arnott, 1979;Short, 1991) surfzone sandbars. These striking patterns in the nearshore display complex behaviour seemingly at odds with their simplicity and rhythmicity.…”