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You are here : eLibrary : IAHR World Congress Proceedings : 36th Congress - The Hague (2015) ALL CONTENT : Sediment management and morphodynamics : 3d numerical simulation of dam break waves over erodible beds: the role of turbulence and mesh size
3d numerical simulation of dam break waves over erodible beds: the role of turbulence and mesh size
Three-Dimensional (3D) numerical simulations of dam-break flows over erodible beds are performed with the open source
Telemac-Mascaret modeling system (www.opentelemac.org). The hydrodynamic model, Telemac-3D, internally coupled
with the sediment transport module Sisyphe, is used. Telemac-3D is based on the solution of the Reynolds Averaged Navier-
Stokes (RANS) equations with a non-hydrostatic pressure distribution. Bed-load rate is calculated using the Meyer-Peter
and Mller (1948) formula with a critical dimensionless shear stress of 0.047. Bed elevation is updated using the sediment
continuity equation. The roughness Manning coefficient is estimated on the basis of the bed material diameter. Resolution
of the governing equations relies on a finite element method on an unstructured mesh of tetrahedral elements. The
computational domain was discretized with prismatic elements, obtained by first dividing the 2D domain with non-overlapping
linear triangles and then by extruding each triangle along the vertical direction into linear prismatic columns that exactly fitted
the bottom and the free-surface. Then, each column was partitioned into non-overlapping layers, requiring that two adjacent
layers comprised the same number of prisms. Emphasis is focused on investigating numerically the effect of turbulence
models and mesh size. In this work, the turbulence stresses are modeled with the aid of the Boussinesq relations and the
performance of four isotropic turbulence closure models is evaluated: the constant viscosity model, the standard kC model,
the Smagorinsky-Lilly subgrid scale model and the mixing length model. Results are compared with published experimental
data on dam-break flows (Fig. 1). Comparisons between numerical results and experimental data are based on water level
evolution measurements at selected gauging stations and bed topography changes. Satisfactory results are obtained using
the standard k- model (Figs. 2 and 3). The mesh refinement (by increasing the number of layers in the vertical direction
and/or the number of nodes in the 2D unstructured triangular horizontal mesh) allows only a slight improvement of the
computed final bed geometry.
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Chapter : IAHR World Congress Proceedings
Category : 36th Congress - The Hague (2015) ALL CONTENT
Article : Sediment management and morphodynamics
Date Published : 28/08/2015
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