Phreatic explosion hazard assessment by numerical simulation

Phreatic explosions (or eruptions) represent very common and dangerous phenomena occurring in active volcanic and geothermal regions. In spite of this, the understanding of their dynamics and the assessment of their hazards are still scarcely known and quantified. In the present work we try to simulate the dynamics of a phreatic explosion by using a transient, two-dimensional, three-phase flow model. Simulations predict the effects of an explosion of a mixture of compressed gases and ground particles into the atmosphere. The governing transport equations of mass, momentum, and energy are solved by a finite difference multifield scheme for both solids and gas phases. We performed several simulations, assuming different initial conditions and system parameters. The model allows analysis of the timewise and spatial distribution of the groundhugging surge generated by the explosion and estimation of its potential hazards in terms of dynamic pressure, ash-in-air concentration, and temperature.