The Role of Coherent Structures in Turbulent Flows

相干结构在湍流中的作用

• 批准号: 61302061
• 负责人: TAMAI Nobuyuki
• 金额: $ 7.1万
• 依托单位: The University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Co-operative Research (A)
• 财政年份: 1986
• 资助国家: 日本
• 起止时间: 1986 至 1987
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-61302061/
• 关键词: Turbulence; Coherent Structure; Inner Layer; Outer Layer; Separation Bubble; Boil; Free Shear-Layer; 混合層; 連行

Coherent sturucture in turbulent flows is a new topic from historical point of view in the research on turbulence. Therefore, the role of coherent structures in hydraulic engineering problems has not been clarified and fully understood yet. A comprehensive study is sought to reach to a unified view and relationships among several problems. The main emphasis is laid on open channel flows and the study consists of two parts. The one is a fundamental part which aims at finding out cherent structures in inner and outer layers in open channel flows. The other is an application part in which the role of coherent vortices in open channel flows and in a shear layer is treated.With simultaneous application of flow visualization techniques and a laser doppler anemometer, spatial and temporal cherent features of longitudinal vortices in an inner layer of an open channel flow were obtained. One to one correspondence between a time siries of signal of velocity and a transverse pattern of longitudinal vortices was found out. Average duration time in the longitudinal direction was specified. For longitudinal vortices in an outer layer, rotational spectrum was utilized. Near the bottom and the water surface, strong correlation was found in two-point probability density of vertical velocity.At a downstream facing step, turbulence structures including pressure and the Reynolds stress were measured. Variation of the separation bubble and the merging of separation eddied are two major triggers to produce kolk-boil eddies at the rear of a step. Three-dimensional structure of separation eddies and horse-shoe vortices in fornt of a hemisphere was clarified. Features of a single vortex and its effect on average velocity fild over a favorable slope were clarified.

从历史的角度来看，湍流的相干结构是湍流研究中的一个新课题。因此，连贯结构在水利工程问题中的作用尚未得到澄清和充分理解。一项全面的研究力求在几个问题之间达成统一的观点和关系。主要重点是明渠流量，研究由两部分组成。一是基础部分，旨在找出明渠水流内层和外层的化学结构。另一个是应用部分，其中处理相干涡在明渠流和剪切层中的作用。同时应用流动可视化技术和激光多普勒风速计，在内层中纵向涡的时空特征获得明渠流量。发现了速度信号的时间序列与纵向涡旋的横向模式之间的一一对应关系。指定了纵向的平均持续时间。对于外层中的纵向涡流，利用旋转谱。在水底和水面附近，垂直速度的两点概率密度存在很强的相关性。在下游台阶处，测量了包括压力和雷诺应力在内的湍流结构。分离气泡的变化和分离涡流的合并是在台阶后部产生科尔克沸腾涡流的两个主要触发因素。阐明了半球形状的分离涡和马蹄涡的三维结构。阐明了单个涡旋的特征及其对有利斜率上平均速度场的影响。

项目成果

中川,祢津,光成,川嶌: 第4回流れの計測大阪シンポジウム. 51-58 (1987)

中川、根津、三成、川岛：第四届流量测量大阪研讨会 51-58（1987 年）。

Nezu, I., Nakagawa, H., Amano, K. and Fujimoto, K.: "Velocity relaxation process of separated step flow and coherent vortex shedding form reattachment in open channel flows" Proc. of the Japanese Conference on Hydraulics. 31. 413-418 (1987)

Nezu, I.、Nakakawa, H.、Amano, K. 和 Fujimoto, K.：“明渠流中分离阶流的速度弛豫过程和相干涡流脱落形成再附着”Proc。

Ikeda, H., Oosako, K., Asaeda, T. and Tamai, N.: "A vertical vortex and boil ober a favorable slope in openchannel flows" Proc. of the Symposium on Turbulence. 19. 210-214 (1987)

Ikeda, H.、Oosako, K.、Asaeda, T. 和 Tamai, N.：“明渠流中有利斜率的垂直涡流和沸腾”Proc。

Oonari, H. et al.: "Lagrangian trace of coherent structures in and inner layer of wall turbulence" Porc. of the Symp. on Turbulence. 19. 205-209 (1987)

Oonari, H. 等人：“壁湍流内层和内层的相干结构的拉格朗日迹”Porc。

祢津家久,中川博次: 土木学会論文集. 369. 89-98 (1986)

Nezu Iehisa，Nakakawa Hirotsugu：日本土木工程师学会会议记录 369. 89-98 (1986)。