Author(s): Nils Reidar B. Olsen; Jochen Aberle; Francisco Nunez-Gonzalez

Linked Author(s): Nils Reidar B. Olsen, Jochen Aberle, Francisco Nunez-Gonzalez

Keywords: Ntidunes; Turbulence; CFD; Numerical modelling; Sediment transport

Abstract: A parametrization of antidunes for CFD computations on a coarse grid is presented. Detailed modelling of the water and turbulence flow over moving antidunes has been carried out, using a fine 2D width-averaged grid. The effect of convective fluxes caused by recirculation zones and other non-uniform characteristics were computed. The data was used to derive a formula for the antidune-induced vertical convection of the water velocities. This formula can be used to take antidunes into account in a CFD model of a longer reach of a river, where the grid is too coarse to resolve the bedforms. The formula increases the flat bed turbulent diffusivity as a function of the antidune height and the depth-averaged water velocity. A test case with a 90o bend is presented, showing that the secondary currents are reduced by applying the new formula.

DOI: https://doi.org/10.3850/IAHR-39WC252171192022578

Year: 2022