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Depth-Averaged Modeling of Flow and Bed Elevation Change in a Curved Channel with Dispersion Stress Terms

Author(s): Tae Beom Kim; Sung-Uk Choi

Linked Author(s): Sung-Uk Choi

Keywords: Depth-averaged model; Bed elevation change; Curved channel; Dispersion stress

Abstract: The flow in curved channels is under the influence of centrifugal acceleration, which induces the secondary flow and the super-elevation in water surface. It is necessary to reflect these three dimensional flow characteristics on the 2D numerical model to simulate more accurately flows in curved channels. The purpose of this study is to develop a 2D finite element model which is capable of predicting the time-dependent flow and bed elevation change. The governing equations are the depthaveraged Reynolds equations for flow fields and the Exner’s equation for bed deformation. In order to consider the secondary flow in curved channels, the effective stress terms are included in the momentum equations. The effective stress terms are composed of the turbulent stress and dispersion stress. The 2D CDG scheme is used for the numerical flow solution and classical BG scheme is used for the solution of Exner’s equation. The developed model is a decoupled model in a sense that the bed elevation does not change simultaneously with the flow during each computational time step. For the accurate estimation of spatial variation of equilibrium sediment load, the effects of the secondary flows in a curved channel and the gravity force due to the geographic change on the direction of sediment transport are taken into account. For validation of flow model, flow experiment data and bed elevation change data in a 180°curved channel are used. At presently, this bed elevation change routine is restricted to the case with uniform sediment, neglecting armoring or grain sorting effects.

DOI:

Year: 2010

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