Modelling the rheology of crystal-magmas
| When |
Sep 16, 2024
from 11:00 to 12:00 |
|---|---|
| Where | Salle des thèses |
| Contact Name | Valérie Vidal |
| Attendees |
Alain Burgisser |
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Magmas are actually immersed granular systems, a mixture of silicate liquid and crystals. We have shown over the years that Computational Fluid Dynamics coupled with Discrete Element Modeling (CDF-DEM) has the potential to represent the rheology of crystal-bearing magmas. The scale of such simulations, however, is small (less than a cubic meter) compared to the cubic kilometer size of natural magmatic systems. The duration of the simulated processes (a few hours) is also regrettably short. To scale up simulation time and size, we propose to define a two-phase flow rheology where the melt is treated as a fluid and the behavior of suspended crystals is averaged into a granular continuous phase. Such an approach has been used in the study of immersed granular systems and many rheology relationships are available in the literature. Using CDF-DEM simulations as a baseline, we show that, unfortunately, the high viscosity in silicate liquids yields dynamical regimes that are not captured by these relationships. We thus used our CDF-DEM simulations to define a new, two-phase flow rheology that includes the full jamming expected to occur in magmas. We then present a two-phase flow model based on this new rheology that has the potential to be scaled up to the size of natural magmatic systems.