Modeling of a gas slug rising in a cylindrical duct and possible applications to volcanic scenarios

The paper deals with the mathematical modelling of a gas slug rising in a cylindrical duct filled with an incompressible liquid. This research is motivated by a phenomenon commonly observed during Strombolian eruptions at basaltic volcanoes, that is, mildly explosive events driven by a large bubble of magmatic gas (a slug) rising up the conduit and bursting at the surface. The model is compared with the laboratory experiments described in [15] and we prove that the constancy of the slug ascent velocity observed in these experiments is fully justifiable. The model is developed both in the case of a Newtonian fluid and in the case of a non-Newtonian power law fluid, more suitable for magmas, and applied to a volcanic scenario.