Hydrodynamic aspects of explosive eruptions of volcanoes: simulation problems

Abstract

The paper offers a short survey of experimental results on simulation of processes of explosive volcano eruptions, based on the method of hydrodynamic pulse shock tubes. The experiments show that the development of cavitation in the magma under the effect of decompression waves is characterized by the formation of bubbly clusters and their transformation into a system of arbitrary distributed slugs as a result of bubble coalescence. As a consequence, the magma flow turns out to be stratified into a system of vertical jets of spatial form, which then disintegrate into individual fragments. An unsteady multiphase mathematical model is created to study the dynamics of the magma state at the initial stage of the explosive eruption. This model takes into account nucleation and diffusive processes, gravity, and dynamically changing viscosity. The results of numerical studies performed within the framework of this model showed that the magma state in 6–7 s (after the beginning of decompression) is characterized by the flow glass transition, if the processes of bubble coalescence are ignored. The flow includes “frozen-in” 0.3-mm-thick bubbles, and the magma viscosity increases by 6–7 orders in the degassing process.