A continuum model of multi-phase reactive transport in igneous systems

Multi-phase reactive transport processes are ubiquitous in igneous systems. A challenging aspect of modelling igneous phenomena is that they range from solid-dominated porous to liquid-dominated suspension flows and therefore entail a wide spectrum of rheological conditions, flow speeds, and length scales. Most previous models have been restricted to the two-phase limits of porous melt transport in deforming, partially molten rock and crystal settling in convecting magma bodies. The goal of this paper is to develop a framework that can capture igneous system from source to surface at all phase proportions including not only rock and melt but also an exsolved volatile phase. Here, we derive an n-phase reactive transport model building on the concepts of Mixture Theory, along with principles of Rational Thermodynamics and procedures of Non-equilibrium Thermodynamics. Our model operates at the macroscopic system scale and requires constitutive relations for fluxes within and transfers between phases, which are the processes that together give rise to reactive transport phenomena. We introduce a phase- and process-wise symmetrical formulation for fluxes and transfers of entropy, mass, momentum, and volume, and propose phenomenological coefficient closures that determine how fluxes and transfers respond to mechanical and thermodynamic forces. Finally, we demonstrate that the known limits of two-phase porous and suspension flow emerge as special cases of our general model and discuss some ramifications for modelling pertinent two- and three-phase flow problems in igneous systems.Comment: Revised preprint submitted for peer-reviewed publication: main text with 8 figures, 1 table; appendix with 3 figures and 2 table

Direct numerical simulations of multiphase flow with applications to basaltic volcanism and planetary evolution

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 243-266).Multiphase flows are an essential component of natural systems: They affect the explosivity of volcanic eruptions, shape the landscape of terrestrial planets, and govern subsurface flow in hydrocarbon reservoirs. Advancing our fundamental understanding and predictive capabilities of multiphase flows is a problem of immense importance for both industrial and scientific purposes. This thesis studies the potential of direct numerical simulations for advancing our fundamental understanding of the multiphase flow dynamics in magmatic flow. It is divided into two parts. The first part investigates gas-fluid coupling during the buoyant ascent of an exsolved gas phase in the conduit of basaltic volcanoes. The second part examines the solidification processes in magma oceans which entail both degassing (gas-fluid coupling) and crystallization (solid-fluid coupling). For both applications, we find that the fluid dynamics at the length scale of the interfaces has important ramifications for the large-scale behavior of the system. We conclude that direct numerical simulations are an interesting complement to more traditional computational approaches and may provide new insights into the complexity of magmatic systems.by Jenny Suckale.Ph.D

Taylor drop in a closed vertical pipe

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Crystal aggregates record the pre-eruptive flow field in the volcanic conduit at Kilauea, Hawaii

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in DiBenedetto, M., Qin, Z., & Suckale, J. Crystal aggregates record the pre-eruptive flow field in the volcanic conduit at Kilauea, Hawaii. Science Advances, 6(49), (2020): eabd4850, doi:10.1126/sciadv.abd4850.Developing reliable, quantitative conduit models that capture the physical processes governing eruptions is hindered by our inability to observe conduit flow directly. The closest we get to direct evidence is testimony imprinted on individual crystals or bubbles in the conduit and preserved by quenching during the eruption. For example, small crystal aggregates in products of the 1959 eruption of Kīlauea Iki, Hawaii contain overgrown olivines separated by large, hydrodynamically unfavorable angles. The common occurrence of these aggregates calls for a flow mechanism that creates this crystal misorientation. Here, we show that the observed aggregates are the result of exposure to a steady wave field in the conduit through a customized, process-based model at the scale of individual crystals. We use this model to infer quantitative attributes of the flow at the time of aggregate formation; notably, the formation of misoriented aggregates is only reproduced in bidirectional, not unidirectional, conduit flow.M.D. acknowledges support the Stanford Gerald J. Lieberman Fellowship and the Postdoctoral Scholarship from Woods Hole Oceanographic Institution

Leveraging Google's Tensor Processing Units for tsunami-risk mitigation planning in the Pacific Northwest and beyond

Tsunami-risk mitigation planning has particular importance for communities like those of the Pacific Northwest, where coastlines are extremely dynamic and a seismically active subduction zone looms large. The challenge does not stop here for risk managers: mitigation options have multiplied since communities have realized the viability and benefits of nature-based solutions. To identify suitable mitigation options for their community, risk managers need the ability to rapidly evaluate several different options through fast and accessible tsunami models, but they may lack high-performance computing infrastructure. The goal of this work is to leverage Google's Tensor Processing Unit (TPU), a high-performance hardware device accessible via the Google Cloud framework, to enable the rapid evaluation of different tsunami-risk mitigation strategies available to all communities. We establish a starting point through a numerical solver of the nonlinear shallow-water equations that uses a fifth-order weighted essentially non-oscillatory method with the Lax–Friedrichs flux splitting and a total variation diminishing third-order Runge–Kutta method for time discretization. We verify numerical solutions through several analytical solutions and benchmarks, reproduce several findings about one particular tsunami-risk mitigation strategy, and model tsunami runup at Crescent City, California whose topography comes from a high-resolution digital elevation model. The direct measurements of the simulation's performance, energy usage, and ease of execution show that our code could be a first step towards a community-based, user-friendly virtual laboratory that can be run by a minimally trained user on the cloud thanks to the ease of use of the Google Cloud platform.</p

Probabilistic seismic hazard assessment for Vanuatu

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