Le prochain VolcaPot aura lieu demain jeudi 26 février à 10h30 en salle JJ.
David Jessop nous présentera ses travaux sur :
« The role of inertial particles and vent geometries in the rise and collapse of volcanic jets »
En espérant vous voir nombreux,
Particle-laden volcanic jets can undergo gravitational collapse to produce ground-hugging pyroclastic density currents or loft material several tens of kilometres. The key to determining which of these two phenomena will occur is the turbulent entrainment of atmospheric air, which adds buoyancy to the jet.
Classical models of eruption columns assume that the entrainment rate is related to the up flow rate of the jet through a coefficient of fixed value, about 10%. In particular, the efficiency of entrainment is assumed to be independent of the vent shape as well as the physical properties of the pyroclastic mixture. However, we show that the presence of inertial particles in the jet can have a significant effect on entrainment due to the additional buoyancy of the particles and the particles altering the size, shape and distribution of the entraining eddies. In conjunction with non-cylindrical vent shapes, we find that inertial particles can increase the entrainment efficiency by nearly a factor of two.