Research highlights : : Coupled CFD-DEM Modeling of Particle-Fluid Interactions in Soil
Fig.1 Practical examples where soil water interactions play a key role.
Coupled CFD/DEM Approach
Interactions between soil particles and pore water underpin important and complex soil behaviors pertaining to the performance of key infrastructures. Landslides and debris flow, piping failure of embankment dams and dredging in coastal areas are amongst outstanding examples (see Fig. 1).
We have developed a coupled Computational Fluid Dynamics and Discrete Element Method (CFD/DEM) tool to simulate the interactions. The tool has been benchmarked by classic geomechanics prolbems including the 1D consolidation problem and the single particle settling in water. It has been further applied to the simulation of sandpiling in water through hopper flow (Fig. 2). Extensive comparison was made of the formed sand piles in dry and wet conditions (Figs. 3). Please refer to the following two papers for detail:
Zhao, J.D., Shan, T. (2013a). Coupled CFD-DEM simulation of fluid-particle interaction in geomechanics. Powder Technology. 239, 248-258. doi: 10.1016/j.powtec.2013.02.003. (PDF)
Zhao, J.D., Shan, T. (2013b). Numerical modeling of fluid-particle interaction in granular media. Theoretical and Applied Mechanics Letters. 3(2): 021007. doi: 10.1063/2.1302107. (PDF)
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| Fig.2 CFD/DEM simulation of sandpiling
via hopper granular flow into a water container (see Zhao and Shan, 2013a)). |
Fig.3 Internal contact force network in
sandpiles formed under dry and wet conditions. |
Fig.4 Simulation of a granular flow impacting on a water reservoir (upper: dry; bottom: wet) (See: Zhao and Shan, 2013c; Shan and Zhao, 2014).
Granular Flow Impacting on Water Basin
Using the coupled CFD/DEM tool, we have further explored the impacting of debris flow onto a water basin and landslide induced trsunami (repulsive waves) (see Fig. 4). In the figure, the upper shows the flow of granular particles into an empty basin, while the bottom displays the impacting of granular flow on a water basin. The following papers provide detail on the simulations and analyses:
Shan, T., Zhao, J.D. (2014). A coupled CFD-DEM analysis of granular flow impacting on water reservoir. Acta Mechanica. 225(8): 2449-2470. doi: 10.1007/s00707-014-1119-z (PDF).
Zhao, J.D., Shan, T. (2013c). The impact of granular flow on a water reservoir - a coupled CFD-DEM study. In Mustoe, G. (ed.) DEM 6: Proceedings of the 6th International Conference on Discrete Element Methods and Related Techniques (August 5-6, 2013, Colorado School of Mines, USA), pp.505-510. (PDF)
Fig.5 Simulation of a mixture of water-particle debris flow impacting on an obstable (upper: debris-water mixture; bottom: purely dry particles).
Simulation of Debris Flow Impacting on a Barrier
The coupled CFD/DEM tool has been further used to simulated the impact of debris flow (granular particle system mixed with water before release, shown in upper figure of Fig. 5) on an barrier, in comparison with a purely dry case (bottome case in Fig. 5). Overall, the water apparent flow faster than the particle flow. And the effect of mixing between the two systems during the flow apparently greatly enhances the mobility of the debris flow as well as its impact on the barrier.
In the future, we aim to further extend the tool to incorporate other processes such as heat and chemical contamination to develop a powerful multiphisics computational platform for relevant practical simulations.
