Author(s): Benoit Spinewine

Linked Author(s):

Keywords: Dam-break; Movable bed; Two-layer shallow-water model; Laboratory experiments

Abstract: Fast geomorphic floods, as resulting from dam- or dike breaks and debris flows, may induce severe soil movements that in turn affect the wave dynamics in terms of arrival times and attained levels. They involve the movement of dense solid-fluid mixtures that may reasonably be assumed to behave as an equivalent continuum. A multi-phase approach is adopted to develop a set of governing equations that rely on a two-layer shallow water description. The proposed framework accounts for granular phase dilatation resulting from grain entrainment across the bed interface, and for the related mass and momentum exchanges induced between the flowing layers. Erosion and deposition derives from a theoretical shock relation, so that the closures for shear stresses at the interfaces govern both frictional losses and geomorphic exchanges in a unified description. The governing equations are solved in a finite volume numerical scheme, both in a 1D version on Cartesian grids and in a 2D version on unstructured triangular meshes. Numerical simulations are faced with results of idealised laboratory experiments of dam-break waves in two configurations: the 1D version is tested against experiments involving a bed profile with an initial discontinuity at the dam location; the 2D version is faced to a sudden valley enlargement in the downstream reach.

DOI:

Year: 2005