Flow structure of bubbles in non-newtonian fluid bu visualization of unsteady stress field

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K20403
• Research Category: Grant-in-Aid for Research Activity Start-up
• Allocation Type: Multi-year Fund
• Review Section: 0301:Mechanics of materials, production engineering, design engineering, fluid engineering, thermal engineering, mechanical dynamics, robotics, aerospace engineering, marine and maritime engineering, and related fields
• Research Institution: Tokyo University of Agriculture and Technology
• Principal Investigator: Kusuno Hiroaki 東京農工大学, 工学(系)研究科(研究院), 特任助教 (90966029)
• Project Period (FY): 2022-08-31 – 2024-03-31
• Keywords: 気泡 / 非ニュートン / 偏光計測

Outline of Final Research Achievements

In this research, the stress field in the vicinity of a bubble was experimentally measured using a polarization measurement technique, which can detect the phase retardation and azimuth angle that would be proportional to the principal stress difference, and the non-Newtonian fluid effect was discussed in turn from the flow structure of a bubble rising in a non-Newtonian fluid.
The validity of the stress measurement results around bubbles in Newtonian fluid using a polarization measurement technique was verified in detail. The results were compared with numerical analysis, and plane stresses were estimated by using an axisymmetric reconstruction method that differs from that used for solids.
In addition, a numerical code that can be applied to various viscoelastic models was developed to validate the polarization measurement around bubbles in viscoelastic fluids with significantly varying bubble rise velocities.

Free Research Field

混相流

Academic Significance and Societal Importance of the Research Achievements

流体の偏光計測手法によって応力積算値を可視化し，軸対称問題であればそれを再構成することで平面応力場を導出することができれば，様々な流体計測が可能になる．また，非ニュートン流体においても，流動構造の違いによって偏光計測のから予想される流動場が異なることから，様々な非ニュートン流体の流動特性の計測に利用できると考えられる．
気泡周りの流動構造を実験的に観測したことにより，その結果は気泡など多くの粘弾性流体特有の流動現象のメカニズム解明や数値解析の検証に用いることができると考えられる．