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2D Two-Layer Shallow-Water Model with a Bank-Failure Operator for Dam-Break Waves on Mobile Beds

Author(s): Catherine Swartenbroekx; Yves Zech; Sandra Soares-Frazao

Linked Author(s): Catherine Swartenbroekx, Sandra Soares-Frazao, Yves Zech

Keywords: No Keywords

Abstract: To consider both bed and bank erosion due to a dam-break induced wave, a bank-failure operator is inserted into a two-dimensional (2D) two-layer shallow-water model. This model accounts explicitly for the inertia of the bed-load transport, considering an upper layer made of clear water and a lower layer, called the bed-load transport layer, made of a mixture of water and moving grains. These layers flow on a motionless bed and are assumed to present distinct depth-averaged velocities. The model accounts for the grain entrainment across the bed interface and for the mass and momentum exchanges between the flowing layers thanks to the definition of an erosion rate. This shallow-water model is solved by a first-order finite-volume scheme on an unstructured triangular mesh. The bank-failure operator consists in comparing locally for each computational cell the bed inclination to the sediment stability angles, considering the impact of a water-level rise as a destabilizing phenomenon. After an erosion or deposition update due to the bed-load transport, the unstable bed elements are tilted around an appropriate axis of rotation, ensuring mass conservation of the assumed homogeneous material. The numerical model is tested for a collapsing circular hole and against laboratory tests of a dam-break flow; firstly in a prismatic channel made of coarse sand, and then over an initial bed step.


Year: 2012

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