Dissertation/Thesis Abstract

Toward Understanding Resonant Volcanic Seismic Signals: Modelling Bubbly Flow in Magma
by Fischer, Brian C., M.S., University of Louisiana at Lafayette, 2017, 51; 10682056
Abstract (Summary)

An important pursuit in volcanology is more accurate predictions of activity. One promising avenue for that pursuit is resonant seismic signals, and the data inherently contained in their resonance. As there is a strong correlation between such signals and the presence of gas, modelling the behavior of gas bubbles within a magmatic system is a critical step in this journey, as well as toward the overall understanding of the volcanic system.

I modelled clusters of bubbles using Boundary Element Method combined with Fast Multiple Method. The bubbles are three-dimensional polygonal meshes with triangular faces. The models are clusters of nearly 1000 bubbles arranged in rectangular prisms of dimensions 18x24x660, run with the long side at various angles, from 0° to 90°, to simulate bubbles nucleated from fresh magma injected into more mature magma. They were allowed to run until the meshes deformed too much, causing errors that render the simulations unviable from that point onward, which is long enough to see different behaviors emerge.

The models presented here show bubbles that behave in accordance with expectations based off of the properties of the Rayleigh-Taylor instability, which causes upwellings to develop in initially level clusters of buoyant materials, and show that above a critical angle of about 30°, the instability disappears. In addition, this behavior also helps explain processes behind Strombolian activity, with clusters above the critical angle developing into a vertical cluster of evenly-spaced plumes, rather than clusters below the critical angle, which develop into plumes at the same height which would reach the surface at roughly the same time.

Indexing (document details)
Advisor: Morra, Gabriele
Commitee: Duex, Timothy, Petculescu, Andi
School: University of Louisiana at Lafayette
Department: Physics
School Location: United States -- Louisiana
Source: MAI 57/05M(E), Masters Abstracts International
Subjects: Geology, Geophysics, Physics
Keywords: Bubbles, Computational modelling, Rayleigh-taylor instability, Strombolian, Volcanology
Publication Number: 10682056
ISBN: 9780355854244
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