JpGU-AGU Joint Meeting 2020

Presentation information

[E] Poster

S (Solid Earth Sciences ) » S-VC Volcanology

[S-VC43] Magma crystallization, fragmentation, and their roles on volcanic eruption

convener:Takahiro Miwa(National research institute for earth science and disaster prevention), Satoshi Okumura(Division of Earth and Planetary Materials Science, Department of Earth Science, Graduate School of Science, Tohoku University), Pranabendu Moitra(University of Arizona)

[SVC43-P01] Estimating the parameter to determine bubble - crystal interaction styles

*Ikeda Kyoko1, Atsushi Toramaru1 (1.Kyushu University, Department of Earth and Planetary Science)

Keywords:analog experiment, bubble-crystal interaction

In the magma, the interaction between suspended crystals and the rising bubble made
by buoyancy is important because the interaction can be expected to control the chemical
evolution of magma chamber and their stratification through the rheological properties
and bulk densities. Beline et al (2010) showed that there are three interaction styles with
changing bubble diameter and viscosity of the liquid by laboratory experiments using an
analog material: a single plastic cube and a controlled single bubble in viscous liquid.
However, the crystal - bubble interaction is still poorly understood since the factors to
make a difference among the three interaction styles are not explained enough. In order
to solve this problem, we give some constraint on the controlling parameters to determine
three interaction styles by analogue experiments.
The experiments are performed in the tank filled with viscous liquid (analog material of
silicate melt)and prepared three different viscosity(0.29 Pa・s, 6.46 Pa・s, 19.1 Pa・s ).
The plastic cube (analog material of crystal) with 10 mm is suspended in liquid by a rod.
The bubble is injected into the liquid from 11cm below the plastic cube from a syringe
connected to a motor controlled by the PC program by which we can change the initial
bubble size. We examine the probability of occurrence of three styles of interaction:
"stuck", "pass", and "split"; "stuck" in which a bubble stays under the solid cube, "pass" in
which a bubble moves around the cube and "split" in which a bubble separated into two
bubbles. To determine the probabilities, we did the repetition of 10 times for the same
condition of initial bubble radii and viscosity.
In our experiments, we observed two styles of the interaction of "stuck" and "pass" and
not "split". It is found that the smaller bubble tends to “stuck”, on the other hand, the
probability of “pass” became higher as the bubble radii are larger. To reveal the boundary
of “stuck” and “pass”, we use Bound number which is a dimensionless number
representing the ratio of bubble relaxation time and the bubble rising time per their radius.
From the results of the examination using the size ratio between solid cube and the final
attached bubble, and Bond number, it is suggested that there are two regimes in the
mechanism of interaction styles. These two different regimes are caused by Reynolds
number which is the ratio of inertia force and viscous resistance. In low Reynolds number
regime is controlled by the final maximum bubble diameter which resulted from
mechanical interaction between bubble and cubes in the higher viscosity. For example, if
the deformed bubble diameter is larger in the horizontal length than the cube width, the
bubble path throws the cube. In high Reynolds number regime is controlled by inertia
force. The probability of occurrence of “pass” is higher as the bubble radius becomes
larger with inertia force.
Thus, we found that there are two regimes in the bubble-crystal interaction style; one
is a static regime (low Re) controlled by the geometrical relation in the horizontal sizes
including static deformation, another is a dynamic regime (high Re) controlled by the
inertia of a rising bubble by buoyancy.