Extreme phenomena of turbulence under strongly stable stratification conditions

强稳定分层条件下湍流的极端现象

• 批准号: 09490029
• 负责人: UEDA Hiromasa
• 金额: $ 6.85万
• 依托单位: KYOTO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1997
• 资助国家: 日本
• 起止时间: 1997 至 1999
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-09490029/
• 关键词: Stratified flow; Turbulence; Stable stratification; Internal gravity wave; Counter gradient diffusion; Turbulent diffusion; Turbulence model; Linear theory; 密度成層; 乱流構造; 乱流渦; 気液界面; レーザー蛍光法; 逆勾配散; PIV

In turbulent flows under extremely strong stably straified conditions flow pattern and diffusion and mixing mechanisms are drastically changed, and transition of turbulent eddy motion into wavy motion plays a substantial role and causes such drastic changes. From this point of view, this research project was aimed to investigate experimentally the characteristics of turbulence and intemal wave and the evolution of internal wavy motion in the stratified turbulent flow and to derive a unified explanation on the extreme phenomena which appear under strong stratification conditions. Extreme phenomena includes counter-gradient diffusion in the vertical direction, and horizontal diffusion and difference between active and passive scalar diffusion mechanisms in the counter-gradient diffusion field.It was found that the counter gradient diffusion and the associated phenomena under strongly stable stratification for zero shear cases was explained quite well by a liner theory. In addition, the theory was extended for the cases when both the shear and stratification exist, and explained such extreme phenomena successfully. It indicates that quite a large part of the extreme phenomena can be considered to be linear processes, although their time evolution is influenced by the initial conditions.Basing upon the new concept mentioned above, a turbulence closure model for the stratified flows was developed in which fluid motion was divided into mean, wave and turbulence components and nonlinear interactions between them were modeled, and the model parameters were determined by the experimental results.

在极强稳定分层条件下的湍流流动中，流型、扩散和混合机制发生了急剧变化，湍流涡动向波动运动的转变起着重要作用，并导致这种急剧变化。本课题正是从这一角度出发，通过实验研究了湍流和内波的特性以及分层湍流内波运动的演化规律，并对强分层条件下出现的极端现象给出了统一的解释。极端现象包括垂直方向上的反梯度扩散、水平方向上的扩散以及反梯度扩散场中主动和被动标量扩散机制的差异，发现零切变情况下强稳定层结下的反梯度扩散及其相关现象可以用线性理论很好地解释。此外，还将该理论推广到同时存在剪切和层结的情况，成功地解释了这种极端现象。基于这一新概念，建立了一个分层流动的湍流封闭模型，将流体运动分解为平均、波动和湍流三个分量，并模拟了它们之间的非线性相互作用，并根据实验结果确定了模型参数。

项目成果

Ueda, H., Takemoto, T., Kim, Y. P. and Sha, W.: "Behavior of Volatile Inorganic Components in Urban Aerosols"Atmospheric Environment. Vol.34. 353-361 (2000)

Ueda, H.、Takemoto, T.、Kim, Y. P. 和 Sha, W.：“城市气溶胶中挥发性无机成分的行为”大气环境。

H. Hanazaki and J. C. R. Hunt: "Linear Processes in Unsteady Stratified Sheared Turbulence"Proc. of IUTAM Symp. on Geometry and Statistics of Turbulence. (1999)

H. Hanazaki 和 J. C. R. Hunt：“非稳态分层剪切湍流中的线性过程”Proc。

Ueda,H: "Photochemical formation and stratospheric intrusion in tropospheric oxidants budget in East Asia" Proc.of Workshop on Transport of Air pollutants in Asia, Laxenburg(IIASA),Austria,27-29 July. 131-140 (1998)

Ueda, H：“东亚对流层氧化剂预算中的光化学形成和平流层入侵”，亚洲空气污染物传输研讨会论文集，奥地利拉克森堡 (IIASA)，7 月 27-29 日。

Hanazaki,H.: "Linear Processes in Unsteady Stratified Sheared Turbulence"Proc.of IUTAM Symp. On Geometry and Statistics of Turbulence. (1999)

Hanazaki,H.：“非定常分层剪切湍流中的线性过程”Proc.of IUTAM Symp。

Karasudani,T.: "Development of a Gas-liquid Equibrator for Estimating CO2 Flux at the Ocean Surface"J.of Atmospheric and Oceanic Technology. vol.16, no.10. 1450-1455 (1999)

Karasudani,T.：“开发用于估算海洋表面二氧化碳通量的气液平衡器”J.of Atmospheric and Oceanic Technology。