2022 Fiscal Year Final Research Report
Temporal and spatial fluctuations of energy transfer and two-dimensional structures spontaneously appearing in three-dimensional turbulence
| Project/Area Number |
19K03677
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 13010:Mathematical physics and fundamental theory of condensed matter physics-related
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| Research Institution | Doshisha University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
佐々木 英一 秋田大学, 理工学研究科, 助教 (60710811)
横山 直人 東京電機大学, 工学部, 教授 (80512730)
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| Project Period (FY) |
2019-04-01 – 2023-03-31
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| Keywords | 局所フラックスベクトル / 異種共存乱流 / カスケード / 臨界平衡 / 波動乱流 / 回転乱流 / 成層乱流 / Charney-Hasegawa-Mima乱流 |
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| Outline of Final Research Achievements |
Small-scale homogeneous isotropic turbulence, large-scale anisotropic structures and wave turbulence coexist in general. Various types of heterogeneous coexistence turbulence are investigated to clarify the relationship between the driving mechanism of structures in real space and the cascades of invariants in wavenumber space.
The transition of 2-dimensional structures appearing in the equatorial and polar regions has been clarified for spherical Couette turbulence. An index to identify the boundary wavenumber among turbulences with different properties has been proposed for 3-dimensional stratified turbulence.
Local-flux vectors to quantitatively investigate anisotropic cascades have been proposed and applied to the energy cascades in 3-dimensional rotating turbulence. The relationship between the anisotropy of the inverse cascades of energy and zonostrophy and the spontaneously appearing zonal flows in the triple cascade has also been clarified in Charney-Hasegawa-Mima turbulence.
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| Free Research Field |
流体物理学
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| Academic Significance and Societal Importance of the Research Achievements |
カスケード理論は一様等方乱流の統計理論の根幹をなし、弱乱流理論は波動乱流の根幹をなすが、回転や成層の効果があると、大スケールに２次元的構造が現れる波動乱流と、小スケールに渦管が現れる一様等方乱流とが共存する。このような異種共存乱流を統一的に理解する理論も評価する定量的手法も無かった。
研究成果の一つである局所フラックスベクトルは、異種乱流の時間スケールが同程度となる領域に沿ってエネルギーがカスケードされるという臨界平衡の予想を初めて定量的に確認したのみならず、エネルギー以外の保存量に対しても波数空間におけるカスケードの非等方化と実空間における大規模構造の生成維持との関係を調べることを可能にした。
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