Modélisation des avalanches denses Approches théorique et numérique

Ancey, Christophe

doi:10.1051/lhb/1994058

Cited by 3 publications

(3 citation statements)

References 15 publications

(6 reference statements)

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“…As viscoplastic models deal with the solid-liquid transition, they also seem relevant for describing basal entrainment: part of the bed may yield under the effects of the normal and shear stresses exerted by the flow, and then be entrained in that flow. This is, for instance, what is thought to happen in snow avalanches [48][49][50].…”

Section: Introductionmentioning

confidence: 78%

The dam-break problem for eroding viscoplastic fluids

Bates

Ancey

2017

Journal of Non-Newtonian Fluid Mechanics

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Natural gravity-driven flows can increase in volume by eroding the bed on which they descend. This process is called basal entrainment and is thought to play a key role in the bulk dynamics of geophysical flows. Although its study is difficult using field measurements, basal entrainment is more easily amenable to analysis using laboratory experiments. We studied basal entrainment by conducting dam-break experiments releasing a fixed amount of viscoplastic fluid (a Herschel-Bulkley fluid) on a sloping, erodible bed of fixed depth. Entrainment was observed continuously, far from the sidewalls, using cameras. Bed material was quickly entrained, which led to flow advancement. Although the slope inclination had clear effects on the entrainment mechanisms, as shown by the internal measurements, this did not translate into faster front progression.Instead, the depth and length of the entrainable material were the most important controlling parameters of front velocity, as the surge scoured out the entrainable layer, pushing the entrainable material downstream and following the rigid bed's geometry. Bulk measurements (front position and flow depth profile) were also compared with predictions from lubrication theory.

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Section: Introductionmentioning

confidence: 78%

The dam-break problem for eroding viscoplastic fluids

Bates

Ancey

2017

Journal of Non-Newtonian Fluid Mechanics

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“…Experiments show that resulting governing equation (12) performs well in the limit of low Reynolds numbers. This process brings to mind other instances of fast basal entrainment of loose material in avalanches 19 and debris flows. 20 It should also be noted that extended Huppert's equation (12) can be cast in a form reminiscent of mass balance equation 1used within the Saint-Venant approach for modeling eroding flows by takingū = −ϱg(h − B) 2 ∂ x h/(3µ) and E = 0 (consistently with our results, which show that basal entrainment occurs instantaneously and so the entrainment rate E should drop to zero).…”

Section: Discussionmentioning

confidence: 99%

“…Among the various scenarios proposed so far, three mechanisms seem most plausible: 7,12,13 (a) entrainment by progressive erosion of the bed along the interface between the flow and streambed, [14][15][16][17] (b) massive entrainment during passage of the front, 18 (c) stepwise or slab-by-slab failure underneath the leading edge. 19,20 Recent field surveys provided evidence that for glaciers and debris flows, the primary mode of entrainment is progressive bed erosion, 21,22 while for snow avalanches, 6,23,24 entrainment occurred within the tip region (mostly by frontal ploughing).…”

Section: Introductionmentioning

confidence: 99%