Large solid motion in dense gas-solid two-phase flows (discrete particle simulation and real-time MRI measurement)

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06081
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Fluid engineering
• Research Institution: Osaka University
• Principal Investigator: Takuya Tsuji 大阪大学, 工学研究科, 准教授 (90379123)
• Research Collaborator: Müller Christoph R.
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 離散粒子シミュレーション / MRI / 固気二相流 / 流動層 / 浮沈 / DEM-CFD / 粉体

Outline of Final Research Achievements

The motion of large solid objects in dense gas-solid flows such as fluidized bed is highly complex due to the influence of surrounding medium particles and gas. In this study, by using numerical simulation based on an original discrete coarse particle model together with nuclear magnetic resonance imaging (MRI) that enables the real-time measurement of granular motions, detailed observation and elucidation of the underlying physics behind the object motions were conducted. Specifically, we focused on the anomalous sphere sinking phenomenon in a particle bed aerated under but close to the minimum fluidization velocity. When the sphere density is close to the apparent density of the bed, local fluidization with bubble formations was observed around the sinking sphere. We revealed that small attenuation of upward fluid force occurring at the moment of bubble detachments from the sphere surface is responsible for the slower and deeper sinking of the sphere.

Free Research Field

流体工学，粉体工学

Academic Significance and Societal Importance of the Research Achievements

気流中に高濃度で固体粒子が分散した高濃度固気二相流は，自然現象や種々の産業装置中に見られる．高濃度固気二層流中に投下された粗大粒子の運動は，大変複雑であるが，高い粒子濃度のため観察自体が困難であり，従来その詳細についてはよくわかっていなかった．本研究では，独自に開発した離散粗大粒子モデルによる数値シミュレーションと，高速MRI計測による実験を併せて実施することにより，高濃度固気二相流中の粗大粒子の運動や周囲の流れについて“見える化”を行い，詳細な観察とこれに基づく現象の理解促進を試みた．本研究の成果は，将来的には高濃度固気二相流が関係する産業装置の最適な設計や運用につながるものである．