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River Morphodynamics for Fast Unsteady Flows Using Coupled Equations Model

Author(s): Khawar Rehman; Tae-Rim Kim; Yong-Sik Cho

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Keywords: River morphodynamics; Dam-break flows; Unsteady flows

Abstract: Fast unsteady flows in case of dam-breaks, torrential rainfalls, and dyke breach carry high energy to which the reaction of river morphology is quite different than under gradually varied flows. To gain an understanding and insight into river morphodynamics we propose a model that is able to approximate unsteady flows in natural rivers, and simulate the associated riverine processes. The governing equations include Saint-Venant equations, continuity equation for sediment flow, and bed deformation equation. Second-order temporal and spatial accuracy is obtained by TVD Runge-Kutta method and high resolution reconstruction techniques, respectively. Coupled equations are solved by Godunovtype finite volume method which is preferred because of its conservation preserving characteristics. Approximate Riemann solver technique of Harten-Lax-van Leer-Contact (HLLC) is used to compute flux components associated with hydrodynamics, and sediment related fluxes are updated by an upwind method. The applicability of the model is tested by simulating dam-break case in an expansion channel; comparisons with experimental values show very satisfactory results showing the accuracy of scheme in simulating flows over erodible beds.

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Year: 2016

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