2019 Fiscal Year Annual Research Report
Flow instabilities in intersecting geometries
| Project/Area Number |
17J00412
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| Research Institution | Okinawa Institute of Science and Technology Graduate University |
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Principal Investigator |
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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| Project Period (FY) |
2017-04-26 – 2020-03-31
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| Keywords | Intersecting flows / Vortex dynamics / Flow instabilities |
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| Outline of Annual Research Achievements |
This year, the focus was on exploring high Reynolds number flow within the cross-slot geometry. Our experimental observations reveal that above a certain critical flow rate (Reynolds number, Re) the flow becomes unstable and a steady vortex flow appears. We discover that by changing the aspect ratio of the cross-section of the geometry and the Re, we can control the number of vortices that appear in the flow field and their structure. We suggested a model based on previous studied to describe the velocity and vorticity profiles of the central vortex. When increasing the Re to a critical value we observed that the flow becomes unsteady and periodic with characteristic frequencies that depends on the aspect ratio of the geometry and on the imposed Re. We have characterized and explained the different mechanisms that govern the periodic fluctuations that are observed in this flow type and our results are supported with numerical simulations done by our collaborators. The manuscript for this work is currently being prepared for submission.
Additionally, at the PMMH lab at ESPCI, we studied the interaction between spherical particles (80 micrometers diameter polystyrene particles, 8% of channels width) and the vortex flow in the cross-slot geometry. Our observations reveal that for a Newtonian fluid the particles will be evenly distributed in the flow field, the particles swirl inside the vortical structure. When adding small amount of polymers, the particles will flow around the vortex and will not be able to swirl through the vortical structure.
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| Research Progress Status |
令和元年度が最終年度であるため、記入しない。
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| Strategy for Future Research Activity |
令和元年度が最終年度であるため、記入しない。
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