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A Semi-Analytical Solution for the Dam-Break Problem over a Movable Bed

Author(s): Luigi Fraccarollo; Aronne Armanini

Linked Author(s): Aronne Armanini

Keywords: Dam-break flow; Bed erosion; Riemann problem; Theoretical solution

Abstract: In the present work a comprehensive theoretical analysis of the Riemann problem for a free-surface flow over a movable bed is carried out. Attention is devoted to the reciprocal interactions between the current and the bed in highly transient conditions. A fully coupled model, where mass and momentum exchanges due to the sediment fluxes are taken into account, is employed. The equilibrium concept has been assumed for the evaluation of the sediment transport in the flow. This study is accomplished through the derivation of the ODE' s expressing the generalised Riemann invariants, which will then be used to compute the solutions. It is here shown that the dry dam-break problem may admit a continuous solution, which, when the equilibrium is represented with a slightly modified version of a classical transport formula, is determined and presented. This solution is controlled by the attitude of the bed to be eroded by the flow, expressed by means of a grain-mobility parameter. Continuous solutions have been found in a range of this parameter. Interestingly enough, when the mobility of the bed tends to be negligibly small and a rigid bed is therefore simulated, the solution tends to reproduce the classical Ritter solution.


Year: 1999

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