LARGE-EDDY SIMULATION OF OSCILLATORY FLOW, SEDIMENT TRANSPORT AND MORPHODYNAMICS OVER RIPPLES

Georgios Leftheriotis, Athanassios Dimas

Abstract


In the present study, a well-resolved large-eddy simulation was coupled to a morphodynamical model in order to study the sediment dynamics induced by an oscillatory flow over a sandy bed, as well as the creation/evolution of ripples under hydrodynamic forcing. The simulations were based on the numerical solution of the Navier-Stokes equations for the flow, empirical formulas for the bed load, and the advection-diffusion equation for the suspended sediment. The evolution of the bed form was obtained by the numerical solution of the conservation of sediment mass equation. The Immersed Boundary method was implemented for the imposition of fluid and sediment boundary conditions on the moving bed surface. The model was effectively validated against laboratory measurements. Results are presented for ripple creation and propagation from a quasi-flat bed, as well as results of ripples adapting to water conditions.

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References


Balaras (2004): Modeling complex boundaries using an external force field on fixed Cartesian grids in large-eddy simulations. Computers & Fluids, vol. 33, pp. 375-404.

Kraft S., Yongqi W., and Oberlack M. (2011): Large eddy simulation of sediment deformation in a turbulent flow by means of level-set method, J. Hydraul. Eng., 137 (11), 1394-1405.

Marieu, V., P. Bonneton, D.L. Foster, and F. Ardhuin. (2008): Modeling of vortex ripple morphodynamics, J. Geophys. Res., 113, C09007.

Nabi M., de Vriend HJ., Mosselman E., Sloff CJ. and Shimizu Y. (2012): Detailed simulation of morphodynamics: 2. Sediment pickup, transport and deposition, Water Resour. Res., 49.

Nielsen (1992): Coastal Bottom Boundary Layers and Sediment Transport. World Scientific, 324pp.

van der Werf, Doucette, O' Donoghue and Ribberink (2007): Detailed measurements of velocities and suspended sand concentrations over full-scale ripples in regular oscillatory flow, J. Geophys. Res., vol. 112, F02012.




DOI: https://doi.org/10.9753/icce.v36.sediment.14