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2018 年度 実績報告書

交差の幾何学における流動不安定性

研究課題

研究課題/領域番号 17J00412
研究機関沖縄科学技術大学院大学

研究代表者

BURSHTEIN Noa Batia  沖縄科学技術大学院大学, 科学技術研究科, 特別研究員(DC1)

研究期間 (年度) 2017-04-26 – 2020-03-31
キーワードVortex dynamics / Vortex confinment / Flow instability / Intersecting geometries
研究実績の概要

This year we have published 2 papers in well known scientific journals. I presented this work in 2 international and 1 domestic conferences.
This past year we have focused on the confinement effect on the onset of symmetry breaking in intersecting geometries.
As we increase the aspect ratio of the cross section of the cross-slot geometry we observe that the critical value in which symmetry breaking occurs is reduced. Our time dependent experiments show that as we impose Reynolds numbers that are close to the critical point, the transition will slow down.
In our well controlled experimental system we found that we can induce merging and splitting of vortices by simply changing the Reynolds numbers of the imposed flow. Vortex dynamics is important in many fields, especially in aerodynamics and turbulent flows.
In our dynamic experiments we found that the merging and splitting of vortices are exponential processes with a rate that depends on the imposed Reynolds number. We show that the confinement of vortices changes the very mechanism in which the merger and splitting process occur.
Additionally, we show that for high aspect ratios where vortices are less confined (confinement is determined by the depth of the geometry), the vortex merging process is faster than the process of vortex splitting. Yet for low aspect ratio where the vortices are highly confined, the merging process is slower than the splitting process. This can be explained by the proximity of the walls that stabilize the flow and act against the vorticity intensification.

現在までの達成度 (区分)
現在までの達成度 (区分)

2: おおむね順調に進展している

理由

The project is advancing though with the new collaboration in ESPCI the direction of the research has slightly shifted, yet the preliminary results show a promising direction.

今後の研究の推進方策

Currently we are exploring high Reynolds number flow within the cross-slot geometry. Initial observations reveal that at a critical Reynolds number the flow becomes unsteady and periodic with a specific frequency that depends on the aspect ratio. The periodic flow occurs for a certain Reynolds number range. Increasing the Reynolds number to higher values results in an unsteady and a-periodic flow that can be described as chaotic. Our collaborators are currently performing numerical simulations to support our findings.
During my internship at the PMMH lab at ESPCI (Paris, France), we are studying the interaction between large spherical particles (80 micrometers diameter polystyrene particles, ~8% of channels width) and the vortex flow in the cross-slot geometry. Initial observations reveal that for a Newtonian fluid the particles will be evenly distributed in the flow field. This is seen for a symmetric flow field as well as for an asymmetric vortex flow (the particles swirl inside the vortical structure). When adding polymer solution (4MD Polyethylene glycol) at a concentration of 100 ppm, the particles will also be evenly distributed in a symmetric flow field. However, once symmetry breaks and a vortex is formed, the particles will flow around the vortex and will not be able to swirl through the vortical structure. Further experiments will be done this year.

  • 研究成果

    (6件)

すべて 2019 2018

すべて 雑誌論文 (2件) 学会発表 (4件)

  • [雑誌論文] 3D-printed glass microfluidics for fluid dynamics and rheology2019

    • 著者名/発表者名
      Noa Burshtein, San To Chan, Kazumi Toda-Peters, Amy Q. Shen, Simon J. Haward
    • 雑誌名

      Current Opinion in Colloid & Interface Science

      巻: 43 ページ: 1-14

    • DOI

      https://doi.org/10.1016/j.cocis.2018.12.005

  • [雑誌論文] Controlled symmetry breaking and vortex dynamics in intersecting flows2019

    • 著者名/発表者名
      Noa Burshtein, Amy Q. Shen, Simon J. Haward
    • 雑誌名

      Physics of fluids

      巻: 31 ページ: 1-13

    • DOI

      https://doi.org/10.1063/1.5087732

  • [学会発表] Inertioelastic flow instability at a stagnation point2019

    • 著者名/発表者名
      Noa Burshtein
    • 学会等名
      Colloidal Science & Metamaterials (CSM 2019), Paris, France
  • [学会発表] Exploring the parameter space around an inertial flow instability at a stagnation point2019

    • 著者名/発表者名
      Noa Burshtein
    • 学会等名
      Faculty of Engineering, University of Liverpool, Liverpool, UK
  • [学会発表] Inertioelastic flow instability at a stagnation point2018

    • 著者名/発表者名
      Noa Burshtein
    • 学会等名
      Flow and Instability of Self-Assembled Systems, OIST, Okinawa, Japan
  • [学会発表] Inertioelastic flow instability at a stagnation point2018

    • 著者名/発表者名
      Noa Burshtein
    • 学会等名
      The American physical Society, Division of Fluid Dynamics meeting, Atlanta, Georgia, USA

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公開日: 2019-12-27  

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