[S-CG46] 地球惑星科学におけるレオロジーと破壊・摩擦の物理

[SCG46-P05] Flow-to-fracture transition of linear Maxwell-type fluid by air injection

*Sanchez Claudia¹、桑野 修²、市原 美恵¹ (1.東京大学地震研究所、2.海洋開発研究機構)

キーワード：火山、マグマ、気泡

Due to decompression during magma ascent, bubbles grow, rise, and burst. These behaviors are coupled with the rheology of the magma. The complex nature of magma and the conditions under which the bubbles develop may control the eruption styles, whether explosive or effusive. Among the complexity, the viscoelasiticy is considered essential for the flow and fracture transition. The linear Maxwell model is the simplest model to represent the magma viscoelasticity. It has a single relaxation time. Brittle fracture of magma is considered to occur when the deformation time scale is shorter than the relaxation time. Although this concept has been used in many eruption models, the ductile-to-brittle transition of flowing fluid has not been sufficiently investigated in the laboratory. We report the experimental study of using an aqueous solution of cetyltrimethylammonium bromide and sodium salicylate (CTAB/NaSal), which forms wormlike micelles known to have a simple Maxwell-type viscoelasticity. We inject air through the fluid and observe the elastic and viscous deformation of the fluid around the bubble. The brittleness of the bubble burst on the fluid surface is characterized by visualizing the elastic strain by the birefringence technic and by measuring the bursting sounds.