| 研究課題/領域番号 |
17J00412
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| 研究機関 | 沖縄科学技術大学院大学 |
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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)
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| 研究期間 (年度) |
2017-04-26 – 2020-03-31
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| キーワード | Microfluidics / Fluid dynamics / Soft matter / Cross-slot |
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| 研究実績の概要 |
Purpose of research - Understanding & characterizing: the onset of instability, the formation and development of flow structures in intersecting geometries and describing them with Landau model. The knowledge gained from these experiments will enable the prediction and control of flow behavior from macro to micro scale systems, with potential applications for industry and academia.
Research plans for this year were met as the plan was to study viscoelasticity effect on spiral vortex formation in the cross-slot
geometry with a microfluidic device with aspect ratio of 1. Study the dynamics of inertial instability with various aspect ratios covering the cases of supercritical and subcritical transitions.
Significance and importance of this FY's achievements:
The effect of viscoelasticity on the spiral vortex instability was thoroughly studied in the cross-slot channel with an aspect ratio of 1.
Our findings are now published in the journals Physical Review X and the Journal of non-Newtonian Fluid Mechanics. The effect of viscoelasticity on the spiral vortex instability that was found in the cross-slot geometry was investigated experimentally and were compared to numerical simulations, and were found to be in qualitative agreement for fluids with low elasticity. The main findings from this part are that increasing elasticity of the fluids causes the flow field to become unstable at lower Reynolds numbers. Our results are significant for the field of drag reduction and improvement of flows.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
1: 当初の計画以上に進展している
理由
Currently, we are summarizing the results for the dynamic experiments of the transition in different aspect ratios (ranging from 0.45 to 2.4). As we change the aspect ratio we observe that the order of the transition changes, from supercritical transition in low aspect ratio to subcritical transition in higher aspect ratio. Our time dependent experiments show that as we impose Reynolds numbers that are close to the critical point, the transition will slow down. Our results are showing similarities to another transition near a tricritical point that was studied in the Taylor-Couette apparatus. We are able to describe the time dependent experiments with the Landau model of phase transitions in an accurate manner.
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| 今後の研究の推進方策 |
In our dynamics experiments we have observed that we can see something very unique which is the controlled merging process of two vortices and we find it to be similar to the merging process in the wake of airplane wings as described in the literature. We can also observe the opposite process, the split of one vortex into two vortices as we reduce the Reynolds number. This is a very difficult experiment and there are only few evidence of vortex splitting in the literature, yet our unique experimental system shows promising preliminary results that will be further investigated.
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