Theory construction and experimental verification for a bubbly flow in a nozzle

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K04179
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 19010:Fluid engineering-related
• Research Institution: Fukuoka Institute of Technology
• Principal Investigator: Egashira Ryu 福岡工業大学, 工学部, 教授 (60455102)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 気泡流 / 気泡 / キャビテーション / ボイド率 / ノズル / 非平衡蒸発

Outline of Final Research Achievements

Theoretical and experimental investigations for a bubbly flow in a nozzle were conducted so that the details of the flow can be revealed. In the theoretical investigation and the numerical calculation, both the nonequilibrium evaporation and condensation at the gas-liquid interface, which have never been taken into account so far, and the translational motion of a single bubble were incorporated. The bubble dynamics analysis was performed for the single bubble translating in a straight circular tube and a tapered circular one, and the results were compared. In the experimental investigation, the distribution of void fraction in the nozzle could be accurately measured by the constant current method with plural ring-shaped electrodes.

Free Research Field

流体力学

Academic Significance and Societal Importance of the Research Achievements

気泡流は原子力発電所の冷却水の流れや，ノズルによるマイクロバブルの生成など，多くの産業分野で見られる．そのような流れを理論的，数値的に調べる際には，気泡の体積割合である「ボイド率」が最も重要なパラメータとなる．本研究成果により，そのボイド率の正確な測定が可能となった．また，まだ単一の気泡に関してではあるが，気泡の気液界面での非平衡蒸発，並進運動を厳密に考慮した理論により，高精度な数値計算が可能となった．