Fluid processes in subduction zones: two-phase flow numerical simulation and observational constraints
Final Report Abstract
Volcanic eruptions demonstrate the spectacular occurrence of magmatic melts as they segregate out of partially molten source regions within the earth, and then ascend through the cold, sub-solidus part of the lithosphere. The processes within the supersolidus source regions are only poorly understood. Here, the objective of the project was placed, first 1D and then 2D analytical and numerical formulations have been developed to describe twophase flow of fluids (melts) rising through a deformable solid matrix. One possible mode of such two-phase flow systems is the development of solitary porosity waves, which could significantly contribute to the ascent of melts and fluids. Thus, the main focus was to systematically investigate the physics and behaviour of such porosity waves by analytical and numerical models. Semi-analytical solutions have been derived for a 1D solitary porosity wave which fit in the governing equations of two phase flow system when the solid phase i.e. the matrix is compacting and has a porosity dependent bulk and shear viscosity. It was found that the background porosity has an important effect. A 1D and 2D Finite Difference code PERCOL2D based on the potential equation formalism of two-phase flow has been developed. It was benchmarked against the 1D analytical solution and the 2D code FDCON using this solitary wave solution as an initial input for porous wave. Systematically, various initial conditions for a porosity wave have been analysed. Lastly numerical modeling has been presented incorporating the parameter of melt network geometry in the effective viscosity formulations of matrix as proposed by Schmeling et al. 2012. New time-dependent and steady state porosity wave dispersion curves have been derived for several more realistic viscosity law, and considerable differences to previously known porosity waves have been found.
Publications
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(2010) : Another 2D code for modeling of twophase flow: A benchmark and an application in geodynamics. — Geodynamik Workshop 2010 in Münster, 6. – 8. Okt. 2010
Kanjilal, S.; Richard, G.; Schmeling, H.
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(2011) : Another 2D code for modeling of twophase flow in geodynamics: Formulation and benchmark. — 8th EGU General Assembly 2011, Vienna, Austria, 3. – 8.4.2011, Poster A37 in GD1.2/TS9.2, Geophysical Research Abstracts, Vol 13, EGU2011-11584
Kanjilal, S.; Richard, G.; Schmeling, H.
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2012: Effective shear and bulk viscosity of partially molten rock based on elastic moduli theory of a fluid filled poroelastic medium. Geophys. J. Int.
Schmeling, H., J.-P. Kruse, and G. Richard
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2012: Solitary-waves in geophysical two-phase viscous media : a semi-analytical solution. Phys. Earth Planet. Int., 198-199 (2012) 61–66
Richard, G. C., S. Kanjilal, H. Schmeling
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2016: Theory and numerical modeling of two phase flow: melt percolation process through porosity dependent viscous matrix inside the Earth. Dissertation, Goethe-Univsrsität Frankfurt
Kanjilal, S.
