Modelling the initiation of a hydrothermal eruption-- the shock tube model : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Mathematics at Massey University, Manawatu Campus, New Zealand
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Date
2011
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Massey University
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Abstract
Modelling of hydrothermal eruption phenomenon has been a growing topic
of research for the past 20 years. To date, models have focussed on the underground
quasi-steady
flow and on the above ground eruption jet including
particle deposition. Very little has been able to be said about the first few
seconds of an eruption, nor has much modelling work been done on eruption
causes. In this thesis we develop a shock tube model for the initiation of a
hydrothermal eruption which aims to answer some of the remaining questions
about causality of a hydrothermal eruption.
The new shock tube model reported in this thesis is the first model able
to simulate the initiation of a hydrothermal eruption. We take into account
the three phases present during the eruption; in the geothermal reservoir below
ground, liquid water and water vapour are present, in the above ground
flow we also include air. The fact that the
flow below ground is moving
through a porous medium is accounted for, and new numerical methods using
the finite volume framework are developed to solve the arising system
of equations. Numerical simulations are described which simulate various
eruptions, including ones with steam caps and rapidly developing cracks in
the geothermal reservoir. Results from numerical simulations will be able to
guide the design of future lab experiments of hydrothermal eruptions. The
work of this thesis results in the first model able to simulate the initiation of
a hydrothermal eruption.
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Keywords
Hydrothermal vents, Hydrothermal eruptions, Hydrothermal explosions, Geothermal reservoirs, Mathematical models, Shock tube model