Transition scenario of multiphase fluid flows described by dispersion rheology

2022 Fiscal Year Final Research Report

• Project/Area Number: 19H02057
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Hokkaido University
• Principal Investigator: Tasaka Yuji 北海道大学, 工学研究院, 准教授 (00419946)
• Co-Investigator(Kenkyū-buntansha): PARK HYUNJIN 北海道大学, 工学研究院, 助教 (00793671) ; 村井 祐一 北海道大学, 工学研究院, 教授 (80273001)
• Project Period (FY): 2019-04-01 – 2023-03-31
• Keywords: 混相流 / 流れの遷移 / レオロジー

Outline of Final Research Achievements

Flow visualization and rheological evaluation of bubble suspensions under unsteady shear were performed for describing transition of multiphase fluid flow including tiny bubbles. In the flow visualization, pipe flow and bubble convection were chosen as flow system to be investigated. In pipe flow visualization, water to be injected as perturbation was contaminated with fluorescent dye to visualize development of perturbation and behavior of bubbles simultaneously. The results indicated that in the case that development of perturbation is accompanied by formation of hair-pin like vortices, tiny bubbles are accumulated by the vortices and enhance generation of local turbulence even at smaller amplitude of perturbation. In the rheological evaluation, liner viscoelastic analysis based on velocity profile measurements indicated variation of the relative viscosity with respect to amplitude and time scale of applied oscillatory shear.

Free Research Field

流体力学

Academic Significance and Societal Importance of the Research Achievements

レイノルズの実験から100年以上の時を経て，流れの遷移研究は結実に向かいつつある．一方で，自然界および工業界で見られる流れの多くが分散相を含む混相流体であり，連続相が作る流れ構造との相互干渉により，その遷移過程は単なる単相流れからの摂動では予測できない．本研究で取り組んだ，分散相の効果をレオロジー物性の変化として捉える手法，ならびに，精緻な可視化観察による乱流遷移初期過程における渦構造と微細気泡の相互干渉の理解は，今後，研究を多方面に拡張する上での重要な考え方，ならびに実例になると考えている．