Paper detail

A model for steady flows of magma-volatile mixtures

A general one-dimensional model for the steady adiabatic motion of liquid-volatile mixtures in vertical ducts with varying cross-section is presented. The liquid contains a dissolved part of the volatile and is assumed to be incompressible and in thermomechanical equilibrium with a perfect gas phase, which is generated by the exsolution of the same volatile. An inverse problem approach is used -- the pressure along the duct is set as an input datum, and the other physical quantities are obtained as output. This fluid-dynamic model is intended as an approximate description of magma-volatile mixture flows of interest to geophysics and planetary sciences. It is implemented as a symbolic code, where each line stands for an analytic expression, whether algebraic or differential, which is managed by the software kernel independently of the numerical value of each variable. The code is versatile and user-friendly and permits to check the consequences of different hypotheses even through its early steps. Only the last step of the code leads to an ODE problem, which is then solved by standard methods. In the present work, the model is applied to the study of two sample cases, representing the ascent of magma-gas mixtures on the Earth and on a Jupiter's satellite, Io. Both cases lead to approximate but realistic descriptions of explosive eruptions, by taking pressure curves as inputs and outputting conduit shapes together with mixture density, temperature and velocity along the ducts.