九州大学-研究者情報 [大貫陽平 (助教) 応用力学研究所附属大気海洋環境研究センター]

海洋内部環境の理解と予測に向けた数理モデリング
キーワード：地球流体力学、海洋力学、非線形力学、内部波、乱流
2017.04.

Wave Topology in Fluids
2021.09～2023.05, 代表者：Antoine Venaille, ENS de Lyon, ENS de Lyon (France)
フランス国立研究機構の助成を受けた流体波動のトポロジーに関する研究プロジェクト。.

Simons Collaboration on Wave Turbulence
2022.01, 代表者：Jalal Shatah, New York University, New York University (USA)
サイモンズ財団の助成を受けた波動乱流に関する国際共同研究プロジェクト。.

回転成層流体における波動現象の多角的理解
2022.04～2024.03, 代表者：大貫陽平, 九州大学応用力学研究所, 九州大学応用力学研究所
地球の海洋大気や各種天体の流体運動における波動現象を主な対象として、分野横断的な基礎研究を推進する。.

海洋潮汐が励起する回転成層乱流のマルチスケール解析
2021.07, 代表者：大貫陽平, 九州大学応用力学研究所
流体物理学に関する世界有数の研究機関に長期間滞在し、理論解析・数値シミュレーション・水槽実験を用いて海洋内部領域における波動や乱流を対象とした基礎研究を実施する。.

深海乱流の励起・散逸を同時に再現可能な領域変形スペクトルモデルの開発
2020.04, 代表者：大貫陽平, 九州大学応用力学研究所
科研費若手研究.

海洋システムの統合的理解に向けた新時代の力学理論の構築
2019.04～2020.03, 代表者：大貫陽平, 九州大学応用力学研究所, 北海道大学低温科学研究所(日本).

東京大学大気海洋研究所気候システム研究系「共同研究」: 海洋深層における乱流拡散のパラメタリゼーション
2018.04～2020.03, 代表者：日比谷　紀之, 東京大学大学院理学系研究科, 東京大学大気海洋研究所
海洋大循環モデルの精度向上に向け、大型計算機システムを用いた理論計算により、潮汐混合パラメタリゼーションの改善を目指す。.

波・流れ・乱流のセンシング・マイニング・モデリング: 流体波動の局所分離解析に関する研究
2018.04～2020.03, 代表者：大貫陽平, 九州大学応用力学研究所, 九州大学応用力学研究所
地球流体力学・核融合プラズマの分野横断研究として、数値モデルデータから各種流体波動を分離し、そのエネルギーフラックスを計算する手法を開発。.

潮汐混合ホットスポットの形成に関わる内部波共鳴現象の解明
2018.04～2020.03, 代表者：大貫陽平, 九州大学応用力学研究所
新学術領域研究「海洋混合学の創設」の一環として実施する公募研究である。
数値モデルと理論解析に基づき。日本南方の深海で生じる潮汐混合過程の理論的解明に取り組んでいる。.

海峡力学過程の統合と解剖
2016.04～2021.03, 代表者：広瀬直毅, 九州大学応用力学研究所
科研費基盤研究(A).

主要原著論文

全てを見る→

1.	Yohei Onuki, Jules Guioth, Freddy Bouchet, Dynamical large deviations for an inhomogeneous wave kinetic theory: linear wave scattering by a random medium, Annales Henri Poincaré: A Journal of Theoretical and Mathematical Physics, doi.org/10.1007/s00023-023-01329-7, 45 pages, 2023.06.
2.	Yohei Onuki, Sylvain Joubaud, Thierry Dauxois, Breaking of internal waves parametrically excited by ageostrophic anticyclonic instability, Journal of Physical Oceanography, doi.org/10.1175/JPO-D-22-0152.1, 53, 6, 1591-1613, 2023.06, A gradient-wind balanced flow with an elliptic streamline parametrically excites internal inertia-gravity waves through ageostrophic anticyclonic instability (AAI). This study numerically investigates the breaking of internal waves and the following turbulence generation resulting from the AAI. In our simulation, we periodically distort the calculation domain following the streamlines of an elliptic vortex and integrate the equations of motion using a Fourier spectral method. This technique enables us to exclude the overall structure of the large-scale vortex from the computation and concentrate on resolving the small-scale waves and turbulence. From a series of experiments, we identify two different scenarios of wave breaking conditioned on the magnitude of the instability growth rate scaled by the buoyancy frequency, λ/N. First, when λ/N ≳ 0.008, the primary wave amplitude excited by AAI quickly goes far beyond the overturning threshold and directly breaks. The resulting state is thus strongly nonlinear turbulence. Second, if λ/N ≲ 0.008, weak wave-wave interactions begin to redistribute energy across frequency space before the primary wave reaches a breaking limit. Then, after a sufficiently long time, the system approaches a Garrett-Munk-like stationary spectrum, in which wave breaking occurs at finer vertical scales. Throughout the experimental conditions, the growth and decay time scales of the primary wave energy are well correlated. However, since the primary wave amplitude reaches a prescribed limit in one scenario but not in the other, the energy dissipation rates exhibit two types of scaling properties. This scaling classification has similarities and differences with D’Asaro and Lien’s (2000) wave-turbulence transition model..
3.	Antoine Venaille, Yohei Onuki, Nicolas Perez, Armand Leclerc, From ray tracing to waves of topological origin in continuous media, SciPost Physics, 10.21468/SciPostPhys.14.4.062, 14, 4, 36 pages, 2023.04.
4.	Yohei Onuki, Irreversible energy extraction from negative temperature two-dimensional turbulence, Physical Review E, 10.1103/PhysRevE.106.064131, 106, 064131, 17 pages, 2022.12.
5.	Yohei Onuki, Sylvain Joubaud, Thierry Dauxois, Simulating turbulent mixing caused by local instability of internal gravity waves, Journal of Fluid Mechanics, 10.1017/jfm.2021.119, 915, A77, 14 pages, 2021.05.
6.	Yohei Onuki, Quasi-local method of wave decomposition in a slowly varying medium, Journal of Fluid Mechanics, 10.1017/jfm.2019.825, 883, A56, 27 pages, 2020.01, [URL], The general asymptotic theory for wave propagation in a slowly varying medium, classically known as the Wentzel–Kramers–Brillouin–Jeffreys (WKBJ) approximation, is revisited here with the aim of constructing a new data diagnostic technique useful in atmospheric and oceanic sciences. Using the Wigner transform, a kind of mapping that associates a linear operator with a function, we analytically decompose a flow field into mutually independent wave signals. This method takes account of the variations in the polarisation relations, an eigenvector that represents the kinematic characteristics of each wave component, so as to project the variables onto their eigenspace quasi-locally. The temporal evolution of a specific mode signal obeys a single wave equation characterised by the dispersion relation that also incorporates the effect from the local gradient in the medium. Combining this method with transport theory and applying them to numerical simulation data, we can detect the transfer of energy or other conserved quantities associated with the propagation of each wave signal in a wide variety of situations..
7.	Yohei Onuki, Yuki Tanaka, Instabilities of Finite-Amplitude Internal Wave Beams, Geophysical Research Letters, 10.1029/2019GL082570, 46, 13, 7527-7535, 2019.07, [URL], Beam-like internal waves are commonly generated by tides in the ocean, but their dissipation processes that cause vertical mixing remain poorly understood. Previous studies examined small-amplitude beams to find that parametric subharmonic instability (PSI) induces latitude-dependent wave dissipation. Using a novel approach based on Floquet theory, this study analyzes the stability of finite-amplitude beams over a wide range of parameters. If beam amplitude is small, PSI is indeed the principal mode under the condition f∕𝜎 ≤ 0.5, where f is the Coriolis parameter and 𝜎 is the beam frequency, and the growth rate is maximum when equality holds. However, as beam amplitude is increased, instability arises even when f∕𝜎 > 0.5, but the location of maximum instability shifts toward lower f∕𝜎; thus, the latitudinal dependence of instability is significantly altered. Furthermore, the resulting energy spectrum is strongly Doppler shifted to higher frequencies, which therefore distinguishes this configuration from the common cases of PSI..
8.	Yohei Onuki, Toshiyuki Hibiya, Parametric subharmonic instability in a narrow-band wave spectrum, Journal of Fluid Mechanics, 10.1017/jfm.2019.44, 865, 247-280, 2019.04, [URL].
9.	Yohei Onuki, Toshiyuki Hibiya, Decay Rates of Internal Tides Estimated by an Improved Wave-Wave Interaction Analysis, Journal of Physical Oceanography, 10.1175/JPO-D-17-0278.1, 48, 11, 2689-2701, 2018.11, [URL], 回転成層流体における波数空間内のエネルギーカスケード過程について、密度成層構造の空間変化や上下境界の影響を取り入れた形で、弱非線形乱流理論に基づく運動学的方程式の定式化を行った。これを用いて、海洋内部で潮汐によって励起された波動が非線形共鳴を経てエネルギーを失う割合を全球的に計算したところ、観測研究に整合する形で、中緯度海域に卓越したエネルギー損失率のピークを再現することに成功した。.
10.	Yohei Onuki, Toshiyuki Hibiya, Excitation mechanism of near-inertial waves in baroclinic tidal flow caused by parametric subharmonic instability, Ocean Dynamics, 10.1007/s10236-014-0789-3, 65, 1, 107-113, 2015.01, [URL].

主要学会発表等

全てを見る→

1.	Yohei Onuki, Sylvain Joubaud, Thierry Dauxois, Breaking of internal waves parametrically excited by ageostrophic anticyclonic instability, 14th European Fluid Mechanics Conference, 2022.09.
2.	大貫陽平, Antoine Venaille, シア流中に励起される内部重力波のスペクトル論的考察, 日本海洋学会2022年度秋季大会, 2022.09.
3.	Yohei Onuki, Sylvain Joubaud, Thierry Dauxois, Simulating turbulent mixing caused by local instability of internal gravity waves, IX International Symposium on Stratified Flows Department of Applied Mathematics and Theoretical Physics, 2022.08.
4.	Yohei Onuki, Sylvain Joubaud, Thierry Dauxois, Breaking of internal waves parametrically excited by ageostrophic anticyclonic instability, Japan Geoscience Union Meeting 2022, 2022.05.
5.	Yohei Onuki, Sylvain Joubaud, Thierry Dauxois, Breaking of internal waves parametrically excited by ageostrophic anticyclonic instability, Ocean Sciences Meeting, 2022.03.
6.	大貫陽平, Sylvain Joubaud, Thierry Dauxois, 楕円渦の内部にパラメトリック励起される重力波の砕波シミュレーション, 日本流体力学会年会 2021, 2021.09.
7.	大貫陽平, Sylvain Joubaud, Thierry Dauxois, 楕円渦の内部にパラメトリック励起される重力波の砕波シミュレーション, 日本海洋学会2021年度秋季大会, 2021.09.
8.	Yohei Onuki, Irreversible energy extraction from negative-temperature two-dimensional turbulence, Japan Geoscience Union Meeting 2021, 2021.06, The formation and transition of patterns observed in various geophysical turbulent flows are commonly explained in terms of statistical mechanics. This study aims to extend the range of such a statistical mechanics theory by introducing a perhaps novel conceptual model. We consider an inviscid two-dimensional flow contained in a bounded domain, the shape of which is distorted by an externally imposed force. Unlike the usual fixed boundary cases, the flow energy within the domain is exchanged with the external system via pressure work through the moving lateral boundary. Concurrently, the flow field remains constrained by vorticity conservation. The vorticity equation expanded onto time-dependent Laplacian eigenfunctions and subsequently truncated at a finite number satisfies Liouville's theorem. Consequently, based on energy and enstrophy constraints, a grand-canonical ensemble (GCE) is defined with a negative or positive temperature. Beginning from the GCE, when the domain shape is distorted from one shape to another in a finite time, the Jarzynski equality is established. The pressure work performed on the system is thus related to the difference in the Helmholtz free energy. The direction of the inequality between the mean work and the free energy difference derived from the Jarzynski equality depends on the sign of the initial temperature. If the temperature is negative, the pressure work irreversibly extracts flow energy from the system. This result provides new insights into the unique thermodynamic characteristics of geophysical flows..
9.	大貫陽平, Sylvain Joubaud, Thierry Dauxois, 内部重力波の局所不安定が引き起こす成層乱流の直接数値シミュレーション, 第34回数値流体力学シンポジウム, 2020.12.
10.	大貫陽平, 負温度を持つ二次元乱流からの不可逆的エネルギー抽出, 日本海洋学会2020年度秋季大会, 2020.11.
11.	Yohei Onuki, Sylvain Joubaud, Thierry Dauxois, Direct numerical simulation of stratified turbulence generated by local instability of internal gravity waves, JpGU - AGU Joint Meeting 2020, 2020.07, With the aim of assessing internal wave-driven mixing in the ocean, we develop a new technique for direct numerical simulations of stratified turbulence. Since the spatial scale of oceanic internal gravity waves is typically much larger than that of turbulence, fully incorporating both in a model would require a high computational cost, and is therefore out of our scope. Alternatively, we cut out a small domain periodically distorted by an unresolved large-scale internal wave and locally simulate the energy cascade to the smallest scales. In this model, even though the Froude number of the outer wave, Fr, is small such that density overturn or shear instability does not occur, a striped pattern of disturbance is exponentially amplified through a parametric subharmonic instability. When the disturbance amplitude grows sufficiently large, secondary instabilities arise and produce much smaller-scale fluctuations. Passing through these two stages, wave energy is transferred into turbulence energy and will be eventually dissipated. Different from the conventional scenarios of vertical shear-induced instabilities, a large part of turbulent potential energy is supplied from the outer wave and directly used for mixing. The mixing coefficient, a ratio between the dissipation rate of kinetic energy and that of available potential energy, is always greater than 0.5 and tends to increase with Fr. Although our results are mostly consistent with the recently proposed scaling relationship between the mixing coefficient and the turbulent Froude number, the values of mixing coefficient obtained here are larger by a factor of about two than previously reported..
12.	Yohei Onuki, Yuki Tanaka, Instabilities of finite-amplitude internal wave beams, Ocean Sciences Meeting 2020, 2020.02.
13.	大貫陽平, Sylvain Joubaud, Thierry Dauxois, 内部波の局所不安定による乱流励起の直接数値シミュレーション, 日本海洋学会2019年度秋季大会, 2019.09.
14.	大貫陽平, 田中祐希, 有限振幅内部波ビームの不安定解析, 日本流体力学会年会2019, 2019.09.
15.	大貫陽平, モノドロミー行列の直接計算による内部波ビームの安定性解析, 日本海洋学会2018年度秋季大会, 2018.09.
16.	Yohei Onuki, Toshiyuki Hibiya, Decay rates of internal tides estimated by an improved wave-wave interaction analysis, Ocean Mixing Gordon Research Conference, 2018.06.
17.	大貫陽平, 地球流体力学における研究ツールとしてのWigner変換, 日本気象学会2018年度春季大会, 2018.05.
18.	Yohei Onuki, Toshiyuki Hibiya, Decay rates of internal tides estimated by an improved wave-wave interaction analysis, Japan Geoscience Union Meeting 2018, 2018.05.
19.	Yohei Onuki, Toshiyuki Hibiya, Theoretical analysis of resonant interaction between internal tides and an internal wave continuum, Ocean Sciences Meeting, 2018.02.
20.	大貫陽平, 海洋力学における研究ツールとしてのWigner変換, 日本海洋学会2017年度秋季大会, 2017.10.
21.	Yohei Onuki, Toshiyuki Hibiya, Theoretical estimates of the intensity of resonant coupling between internal tides and internal waves in the western Pacific, The 19th Pacific-Asian Marginal Seas (PAMS) Meeting, 2017.04.
22.	大貫陽平, 日比谷紀之, 統計流体力学に基づく潮汐混合パラメタリゼーションの試み, 日本海洋学会2016年度秋季大会, 2016.09.
23.	Yohei Onuki, Toshiyuki Hibiya, Geography of the attenuation rates of baroclinic tidal energy estimated using wave-wave interaction theory, Japan Geoscience Union Meeting 2016, 2016.05.
24.	大貫陽平, 日比谷紀之, Parametric Subharmonic Instability の統一理論, 日本海洋学会2016年度春季大会, 2016.03.
25.	Yohei Onuki, Toshiyuki Hibiya, Estimates of the attenuation rates of baroclinic tidal energy caused by resonant interactions among internal waves based on the weak turbulence theory, Ocean Sciences Meeting, 2016.02.
26.	Yohei Onuki, Toshiyuki Hibiya, Estimates of the attenuation rates of baroclinic tidal waves caused by resonant interactions with the background internal wave continuum, International Union of Geodesy and Geophysics 26th General Assembly, 2015.06.
27.	大貫陽平, 日比谷紀之, 遠方伝播する傾圧潮汐波の波動間相互作用による散逸過程, 日本海洋学会 2015年度春季大会, 2015.03.
28.	Yohei Onuki, Toshiyuki Hibiya, Excitation Mechanism of Near-inertial Currents in Baroclinic Tidal Flow Caused by Parametric Subharmonic Instability, Asia Oceania Geosciences Society Annual 11th Meeting, 2014.08.
29.	大貫陽平, 日比谷紀之, 内部潮汐流から近慣性流へエネルギーを輸送するPSIの増幅機構に関する理論的研究, 日本海洋学会2013年度春季大会, 2013.03.

所属学会名

日本地球惑星科学連合

日本海洋学会

学会大会・会議・シンポジウム等における役割

2023.02.14～2023.02.16, Eddies and Waves: Theory, Models, and Observations, Chair.

2022.08.29～2022.09.01, IX International Symposium on Stratified Flows Department of Applied Mathematics and Theoretical Physics, Chair.

2021.09.13～2021.09.17, 日本海洋学会 2021年度秋季大会, 座長.

2020.11.27～2020.11.29, 日本海洋学会 2020年度秋季大会, 座長.

2019.08.25～2019.08.27, 新海洋混合学OMIX若手会サマースクール, 世話人.

2018.09.03～2018.09.04, The 15th Korea-Japan (Japan-Korea) Joint Seminar in the Ocean and the Atmosphere, 座長.

学術論文等の審査

年度	外国語雑誌査読論文数	日本語雑誌査読論文数	国際会議録査読論文数	国内会議録査読論文数	合計
2023年度	1				1
2022年度	4	0	0	0	4
2021年度	2	1	0	0	3
2020年度	3	0	0	0	3
2019年度	5	0	0	0	5
2018年度	0	0	0	0	0
2017年度	1	0	0	0	1

海外渡航状況, 海外での教育研究歴

Indian Institute of Technology Madras, India, 2022.08～2022.08.

École normale supérieure de Lyon, France, 2021.07～2023.06.

École normale supérieure de Lyon, France, 2019.06～2019.07.

École normale supérieure de Lyon, France, 2019.03～2019.03.

Hamburg University, Germany, 2019.02～2019.02.

Applied Physics Laboratory, University of Washington, UnitedStatesofAmerica, 2018.06～2018.06.

Woods Hole Oceanographic Institution, UnitedStatesofAmerica, 2018.06～2018.06.

2nd International Symposium “Ocean Mixing Processes: Impact on Biogeochemistry, Climate and Ecosystem”, Poster presentation award, 新学術領域研究（研究領域提案型）　領域番号4702 新海洋混合学, 2018.10.

日本海洋学会2016年度秋季大会若手優秀発表賞, 日本海洋学会2016年度秋季大会実行委員会, 2016.09.

日本海洋学会2016年度春季大会若手優秀発表賞, 日本海洋学会2016年度春季大会実行委員会, 2016.03.

平成29年度研究奨励賞, 東京大学大学院理学系研究科, 2017.03.

平成26年度研究奨励賞, 東京大学大学院理学系研究科, 2014.03.

科学研究費補助金の採択状況(文部科学省、日本学術振興会)

2020年度～2023年度, 若手研究, 代表, 深海乱流の励起・散逸を同時に再現可能な領域変形スペクトルモデルの開発.

2018年度～2020年度, 新学術領域研究, 代表, 潮汐混合ホットスポットの形成に関わる内部波共鳴現象の解明.

2016年度～2020年度, 基盤研究(A), 分担, 海峡力学過程の統合と解剖.

日本学術振興会への採択状況(科学研究費補助金以外)

2021年度～2023年度, 海外特別研究員, 代表, 海洋潮汐が励起する回転成層乱流のマルチスケール解析.

2015年度～2016年度, 特別研究員, 代表, 海洋内部における力学的階層構造の詳細解明に向けた理論的研究.

共同研究、受託研究(競争的資金を除く)の受入状況

2023.04～2024.03, 分担, Triadic resonant instability of internal gravity waves in a stratified shear flow.

2023.04～2024.03, 分担, Small-scale instabilities in rotating and stratified fluid.

2022.04～2023.03, 分担, Energy cascade and mixing due to internal wave in stratified fluid.

2022.04～2024.03, 分担, Nonlinear energy transfer within the oceanic internal wave field.

2022.04～2024.03, 分担, 金星大気波動の解析.

2022.04～2024.03, 分担, Quasi-resonance phenomena in geophysical waves.

2021.04～2022.03, 連携, 非平衡開放システムにおける時空間ダイナミクスの研究.

2021.04～2022.03, 代表, 流体波動の局所分離と不安定解析に関する研究.

2019.04～2020.03, 代表, 海洋システムの統合的理解に向けた新時代の力学理論の構築.

2018.04～2019.03, 分担, 黒潮大蛇行を引き起こす膠州海山における傾圧不安定の発達過程.

2018.04～2020.03, 代表, 流体波動の局所分離解析に関する研究.


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