2018 Fiscal Year Final Research Report
On global stability and large-scale intermittent structures in subcritical wall-turbulence transition and complex fluid flows
| Project/Area Number |
16H06066
|
|---|
| Research Category |
Grant-in-Aid for Young Scientists (A)
|
| Allocation Type | Single-year Grants |
|---|
| Research Field |
Fluid engineering
|
|---|
| Research Institution | Tokyo University of Science |
|---|
Principal Investigator |
|
|---|
| Project Period (FY) |
2016-04-01 – 2019-03-31
|
| Keywords | 亜臨界遷移 / 壁乱流 / DNS / 乱流縞 / 粘弾性流体 |
|---|
| Outline of Final Research Achievements |
The importance of localized turbulence has been noted in the subcritical transition between laminar state and turbulent state of the flow. In this study, large-scale intermittent structures, or spatial patterns, formed by localized turbulence in the vicinity of the limit where turbulence can be maintained are investigated by numerical simulation and visualization experiments for wall turbulence. The robustness of large-scale intermittent structure in complicated flows, such as flows on rough wall surface, viscoelastic fluid flows, and solid-liquid two-phase flows, and the lower critical Reynolds number (global instability) and its dependencies on control parameters were examined. In particular, the the universality of turbulent stripe (stripy patterns oblique to the main flow direction) was discussed.
|
| Free Research Field |
流体工学
|
| Academic Significance and Societal Importance of the Research Achievements |
流体力学の未解決問題の一つ「亜臨界乱流遷移」の解明は，乱流起源を探る理学的興味に加えて，流体機器の乱流制御という工学的重要性から，長年切望されてきた．例えば，熱交換器内で（乱流遷移の）臨界に近い流動状態がしばしば現れるが，層流化や乱流化または混在した間欠的な場を維持するかで流動/伝熱特性が大幅に変化する事象がある．亜臨界状態の予測や制御が可能となれば，高効率で安全な混合や熱伝達を促進する技術開発に繋がるものと期待できる．
|
