Control of local flow structure of viscoelastic fluid in the vicinity of bubble interface using pressure-oscillation field and its application

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K04285
• 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: Nagoya Institute of Technology
• Principal Investigator: Shuichi Iwata 名古屋工業大学, 工学(系)研究科(研究院), 教授 (00293738)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: viscoelastic fluid / flow birefringence / negative wake

Outline of Final Research Achievements

Rheological properties of the 3wt% aqueous gelatin solution under the same cooling condition in the Quette flow geometry is simultaneously measured by following two ways; (i) measuring dynamic viscoelasticity by the stress-controlled rheometer and (ii) 2D retardation profile by the 2D high-speed polarization camera. The stress profile can be estimated by combining the two sets of results, (i) and (ii). It is shown that the stress around the long tail behind the cuspidal air bubble is much higher than that around the cuspidal bubble. We also evaluated effects of viscoelasticity and local flow surrounding the tiny bubble shape under bigger pressure-oscillating field in the viscoelastic fluids. Strong vertical retardation due to the orientation of the fluid occurs as a result of local stress at rim (edge) of the bubble during the contraction phase, and a weak retardation occurs near the bubble surface due to biaxial deformation of the surrounding fluid during the expansion phase.

Free Research Field

非ニュートン流体力学

Academic Significance and Societal Importance of the Research Achievements

粘弾性流体中で形成される特異な形状を示す界面には，強い応力が作用していることを流動複屈折と応力制御式レオメーター測定のその場観察より明らかになった．また，圧力振動場では，気泡を真球形状に復元する表面張力よりもさらに強い応力が作用し，特異な形状を示すことが示された．本研究の成果は，印加する圧力振動条件の操作により弾性応力を制御し，気泡形状を操作することが可能であることを示した．産業界では，粘弾性流体から気泡を除去するニーズは大きい．今回の成果は，圧力振動場を活用した気泡除去の制御方法への活用が期待される．