Multi-Particle Numerical Simulations Of Collapsing Volcanic Columns

A multi-particle thermo-fluid dynamic model was developed to assess the dynamics of the transient twodimensional behavior of collapsing columns and associated pyroclastic currents. The model accounts for mechanical and thermal interactions between a continuous gas phase and N solid dispersed phases, each characterized by specific physical parameters and properties. The dynamics of the process were simulated by adopting a RANS approach, able to resolve the main features of the flow, as well as turbulence and fluidization. Numerical simulations were carried out by using the computer code GMFIX. These describe the formation of the vertical jet, the column collapse (namely, the building of the pyroclastic fountain), the generation of radial spreading pyroclastic current, and the development of thermal convective instabilities from the whole flow. In particular, pyroclastic currents were described as formed by a dilute fine-rich suspension current overlying a dense underflow rich in coarse particles