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https://hdl.handle.net/20.500.14094/90007792
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2024-04-26
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90007792 (fulltext)
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メタデータID
90007792
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open access
出版タイプ
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タイトル
Rheology of a dilute ferrofluid droplet suspension in shear flow: Viscosity and normal stress differences
著者
著者ID
A2486
研究者ID
1000080824169
KUID
https://kuid-rm-web.ofc.kobe-u.ac.jp/search/detail?systemId=c1445de1435393e1520e17560c007669
著者名
Ishida, Shunichi
石田, 駿一
イシダ, シュンイチ
所属機関名
工学研究科
著者名
Matsunaga, Daiki
収録物名
Physical Review Fluids
巻(号)
5(12)
ページ
123603-123603
出版者
American Physical Society (APS)
刊行日
2020-12-15
公開日
2021-01-26
抄録
We report the rheology of a dilute ferrofluid droplet suspension under simple shear flow, using the three-dimensional lattice-Boltzmann simulation and the phase-field model. In our simulation, we utilize 12M computational grids to fully resolve the droplet deformation, and GPU parallelization is used to speed up the computation. The droplet deformation is determined by both the background shear flow and the external magnetic field effects. The ferrofluid droplet has a character to elongate in the direction of the external field, and a uniform static magnetic field is applied to the system to control the droplet shape. By changing the external field strength and direction, we found that the suspension rheologies can be drastically modified. The viscosity increase (decrease) with the external field when the external field is applied to the velocity gradient direction (velocity direction). Just by imposing the external magnetic field, the specific viscosity becomes 12∼620% of the viscosity under no external magnetic field. The magnetic force is also practical to control the normal stresses, since the normal stress in ith direction decreases when the magnetic field is applied to the ith direction. Therefore, in order to increase (decrease) the first normal stress difference N1, the external magnetic field should be applied to the velocity direction (velocity gradient direction). To increase (decrease) the second normal stress difference N2, the external magnetic field should be applied to the velocity gradient direction (vorticity direction). By applying the magnetic field, we also show that the normal stresses N1, N2 even show opposite sign from the normal droplet solution (N1>0, N2<0) under small-Reynolds-number conditions. Our work suggests that the ferrofluid droplet would be a practical complex fluid to control the suspension properties, just by changing the external magnetic field strength and directions.
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工学研究科
学術雑誌論文
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© 2020 American Physical Society
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資源タイプ
journal article
言語
English (英語)
eISSN
2469-990X
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関連情報
DOI
https://doi.org/10.1103/PhysRevFluids.5.123603
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