Author(s): Alex Ghaitanellis, Damien Violeau, Agnes Leroy, Martin Ferrand, Antoine Joly, Kamal El Kadi Abderrezzak
Linked Author(s): Alex Ghaitanellis
Keywords: Sediment transport, scouring, non-newtonian, Smoothed Particle Hydrodynamics (SPH)
Abstract:
A multi-fluid SPH formulation combined to an elastic-viscoplastic stress model is applied to the modelling of non-cohesive sediment transport. The multi-fluid formulation is based on Hu and Adam's (2006) model using a modified continuity equation proposed by Vila (1999) so that the model is able to handle free-surface flows. The boundary conditions are imposed using the unified semi-analytical wall (USAW) boundary conditions model that has proved its efficiency in simulating flows that both require an accurate pressure and shear stress treatment at the wall, and present complex boundary geometries (Ferrand et al., 2013). The sediment is assumed to be either dry or fully saturated and the water-sediment mixture is modelled using a continuous description. Regarding the deviatoric stresses, the soil is assumed to behave as an elastic material when the strain rates are low, similarly to Ulrich (2013). Otherwise, it behaves as a viscoplastic fluid for non-negligible strain rates. Hence, the material has a yield stress under which no significant deformation occurs. When it is exceeded, the soil starts to flow following a shear thinning rheological law. The transition between solid and liquid state is made using a blending function driven by the magnitude of strain rate. A new liquid-solid transition threshold based on the granular material properties is proposed, making the model free of numerical parameter. A particular attention is paid to the computation of the yield stress that has a key role in the solidliquid transition as well as in the rheological behaviour of the non-Newtonian fluid state. The model is tested on 2D soil collapse test case and a dam break over mobile bed where the rapid transient flow involves erosion of sediment and bed-load transport. Results are compared with experimental data (Bui et al., 2008; Spinewine and Zech, 2007) and a good agreement is obtained. (2595-72-347)
Year: 2017