权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

The dynamics of coherent structures in developed turbulence

发达湍流中相干结构的动力学

基本信息

批准号：
08640505
负责人：
TOH Sadayoshi
金额：
$ 1.6万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

I obtained mainly the following three results on the dynamics and the structures in developed turbulence.1. In two-dimensional free convection (FC) turbulence, entropy cascade governs turbulent transfers in scales. Entropy cascade is intermittent like energy cascade in three dimensional Navier-Stokes turbulence. I have determined the exponents of structure of functions of temperature differences and velocity differences in terms of ESS (Extended Self-Similarity) hypothesis. As a result, it is shown that ESS method works well even for the free convection system and gives plausible results. However, the intermittency observed is not explained by the existing models. This is because the existing models are based on the intermittency of the dissipation rate and deal with directly the statistics of the velocity differences. and temperature differences. I am trying to construct a new model.2. I have examined the intermittency of entropy cascade from the dynamical perspective focusing on its character-istic times. It is shown that the large fluctuations which seem to cause the intermittency and are observed as structures, highly correlate both in time and scale and fluctuations of their correlation times are weak. These large fluctuations On the other hand, homogeneous fluctuations which are the background of the structures, contain the greater part of the entropy of the system. The scaling of their average over space determines the characteristic times of the intermittency or the structures.3. In channel flow turbulence, Iproposed the definition of streak by which whole structure of streak from the viscous sub-layr to the log-layr is well visualized. The importance of the roll of structures in the viscous sub-layr is examined. It is also shown that the dynamics of the boundary layr is explained by the dynamics of streak. The three dimensional structure of streaks observed in their evolutions is explained by the simple argument based on the symmetry of the configuration.

主要得到了以下三个关于发展双折射的动力学和结构的结果.在二维自由对流（FC）湍流中，熵级联控制着尺度上的湍流传递。在三维Navier-Stokes湍流中，熵级联类似于能量级联。根据ESS（Extended Self-Similarity）假设，确定了温差和速度差函数的结构指数。结果表明，ESS方法即使对自由对流系统也是有效的，并给出了合理的结果。然而，现有的模型不能解释观察到的不稳定性。这是因为现有的模型都是基于耗散率的不确定性，直接处理速度差的统计。和温度差异。我正试图建立一个新的模型。本文从动力学的角度考察了熵级联的不稳定性，着重分析了其特征时间。结果表明，似乎引起不稳定性并被观测为结构的大起伏在时间和尺度上都高度相关，它们的相关时间的起伏很弱。另一方面，作为结构背景的均匀涨落包含了系统的大部分熵。它们在空间上的平均值的标度决定了不连续性或结构的特征时间。在槽道流湍流中，我提出了条纹的概念，使条纹从粘性亚层到对数层的整体结构形象化。研究了粘性子层中结构滚动的重要性。边界层的动力学可以用条纹动力学来解释。在其演变中观察到的条纹的三维结构解释的简单的论点的基础上的对称性的配置。