Opening of a System of Cracks – on the Mechanism of Cyclic Lateral Eruption of the St. Helens Volcano in 1980
V. K. Kedrinskii1, M. N. Davydov1, A. A. Pilnik2, A. A. Chernov1,2
1Lavrentyev Institute of Hydrodynamics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
2Kutateladze Institute of Thermophysics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090, Russia
Keywords: магматический расплав, волна декомпрессии, многофазная математическая модель, кавитация, вязкость, пограничный слой, щелевое вулканическое извержение, magma melt, decompression wave, multiphase mathematical model, cavitation, viscosity, boundary layer, slotted volcanic eruption
Abstract
The dynamic behavior of a magma melt filling a slotted channel (crack) in a closed explosive hydrodynamic structure is considered. The explosive hydrodynamic structure includes the volcano focal point with a connected vertical channel (conduit) closed by a plug and a system of internal cracks (dikes) near the dome, as well as a crater open to the atmosphere. A two-dimensional model of a slotted eruption is constructed with the use of the Iordanskii-Kogarko-van Wijngaarden mathematical model of two-phase media and the kinetics that describes the basic physical processes in a heavy magma saturated by the gas behind the decompression wave front. A numerical scheme is developed for analyzing the influence of the boundary conditions on the conduit walls and scale factors on the melt flow structure, the role of viscosity in static modes, and dynamic formulations with allowance for diffusion processes and increasing (by several orders of magnitude) viscosity. Results of the numerical analysis of the initial stage of cavitation process evolution are discussed.
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