Yuri Sobral - Collapse of immersed granular columns
|2 October 2019
|14:00 - 14:50
|What is it:
|Department of Mathematics
|Who is it for:
|University staff, External researchers, Current University students
Yuri Dumaresq Sobral (University of Brasilia) joins us for the Physical Applied Mathematics Series. Note the unusual room - 5.210 in University Place.
The collapse of granular columns in a viscous fluid is a common model case for submarine geophysical flows. In a column collapse, an initial granular column of grains is suddenly put into motion by gravity, which then spreads and deposits over a certain runout distance. In dry collapses, the initial aspect ratio of the column is known to be the major controlling parameter of the final runout. However, when the granular column is immersed in a fluid, this problem is not yet fully understood. This talk addresses two major parameters, i.e., the initial aspect ratio and the initial packing density, based on two types of fluid-particle coupling schemes. In the first part of this talk, results on local-averaged fluid-particle simulations for a wide range of initial aspect ratios will be presented. Both similar and distinct features are observed in immersed collapses compared to their dry counterparts. Underwater collapses for large aspect ratios exhibit unique dynamics as the eddies generated in water erode the surface of the granular layer, thus modifying the deposit morphology. The influence of the sample size and of the model parameters will also be discussed. In the second part, an investigation of the influence of packing density based on pore-scale direct numerical simulations will be presented. Dense packings result in slow dynamics and short runout distances, while loose packings are associated with fast dynamics and long runout distances. The simulations provide micromechanical evidence of the pore pressure feedback mechanism on the triggering and runout stages of the immersed granular collapse. Comparisons with results obtained over a wide range of length scales, including small-scale numerical and experimental data and large-scale field data, will be presented.
Organisation: University of Brasilia
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