Abstract
We simulate here the collapse of granular columns immersed in a viscous fluid based on a simplified version of the model developed by [2]. The simulation quite well reproduces the dynamics and deposit of the granular mass as well as the excess pore fluid pressure measured in the laboratory experiments of [10] owing that dilatancy effects and pore pressure feedback are accounted for. In particular, the difference in the behaviour of initially loose and dense columns is reproduced numerically.
Highlights
Describing grain/fluid interaction in debris flows models is still an open and challenging issue with important impact on hazard assessment [3, 7]
The system of mass and momentum conservation equations from Jackson’s model is closed by a weak compressibility relation following [11]. This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value
The two-layer two-phase solid/fluid model introduced in [2] is solved here numerically in the case of immersed granular flows. This thin-layer depth-averaged model makes it possible for the fluid to be either expelled from or sucked into the mixture at its upper boundary depending on the compression or dilation of the granular phase
Summary
Describing grain/fluid interaction in debris flows models is still an open and challenging issue with important impact on hazard assessment [3, 7]. The system of mass and momentum conservation equations from Jackson’s model is closed by a weak compressibility relation following [11] This relation implies that the occurrence of dilation or contraction of the granular material in the model depends on whether the solid volume fraction is respectively higher or lower than a critical value. To simulate underwater granular flows, we consider the following simplifications: (i) we rewrite the hydrostatic pressure terms in the momentum equations by using the hypothesis of horizontal free surface: hm(t, x) + h f (t, x) + b(x) + xtan θ = cst (Figure 1) and (ii) we neglect the friction between the upper fluid layer and the mixture layer.
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