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Clarification of Diffusion Phenomena in the Turbulent Field Including Large-Scale Eddies (Particle Diffusion in Turbulent Shear Flows)

澄清包含大尺度涡流的湍流场中的扩散现象（湍流剪切流中的粒子扩散）

基本信息

批准号：
60550122
负责人：
MAKITA Hideharu
金额：
$ 1.28万
依托单位：
Toyohashi University of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1985
资助国家：
日本
起止时间：
1985 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-60550122/
关键词：
Turbulent Diffusion Anisotropic Turbulence Velocity Distribution Scale レイノルズ数

项目摘要

A turbulence generator and a velocity distribution generator were developed in order to enable to simulate the atmospheric turbulence in a small wind tunnel. The particle diffusion was investigated in a strong turbulence fields generated by the equipments. The results were as follows,(1): In the turbulence field, the turbulence intensities exceeded 10 % and the longitudinal integral length scale was more than five times as large as the mesh size of the generator. Inertial subrange of more than two orders in wave number was observed in the spectrum of the large scale turbulence. The characteristic features of the large scale turbulence were similar to those of a turbulence of Re = <10^6> though Re = <10^4> .(2): The coherent vortices formed downstream of the two-dimensional bodies were irregularly weakened or intensified by the large scale turbulence and the vortex streets meandered. The magnitude of the maximum velocity defect of the wake in the large scale turbulence was smaller than that in the grid turbulence. And the half-value width of the velocity defects was enlarged in the large scale turbulence.(3): A three-dimensional anisotropic turbulence and an axisymmetric turbulence were generated by installing a slit and a honeycomb downstream of the turbulence generator. The process of the return to isotropy was expressed by the theoretical model.(4): The velocity distribution generator was able to form arbitrary profiles of vertical velocity distributions in its downstream region in the test section. The horizontal distribution of the turbulence was almost homogeneous.(5): The particles rapidly diffused and the width of distribution of these concentration was enlarged in the large scale turbulence field. The eddy diffusivity was 270 <mm^2> /s in the weak turbulence and 7300 <mm^2> /s in the large scale turbulence. In the turbulent shear flow, the concentration distribution leaned to the side of lower velocity.

开发了湍流发生器和速度分布发生器，以便能够模拟小型风洞中的大气湍流。在设备产生的强湍流场中研究了颗粒扩散。结果表明:(1):在湍流场中,湍流强度超过10%,纵向积分长度尺度达到发电机网格尺寸的5倍以上。在大尺度湍流的频谱中观察到波数超过两个数量级的惯性子范围。尽管Re = <10^4>，但大尺度湍流的特征与Re = <10^6>的湍流相似。(2)：二维体下游形成的相干涡流被大尺度湍流不规则地减弱或增强，涡街蜿蜒。大尺度湍流中尾流最大速度缺陷的大小小于网格湍流中的尾流最大速度缺陷的大小。并且在大尺度湍流中速度缺陷的半值宽度增大。(3)：通过在湍流发生器下游安装狭缝和蜂窝结构，产生三维各向异性湍流和轴对称湍流。理论模型表达了恢复各向同性的过程。(4)：速度分布发生器能够在测试段的下游区域形成任意的垂直速度分布剖面。湍流的水平分布几乎是均匀的。(5)：在大尺度湍流场中，颗粒迅速扩散，浓度分布宽度扩大。弱湍流中涡流扩散率为270<mm^2>/s，大尺度湍流中涡流扩散率为7300<mm^2>/s。在湍流剪切流中，浓度分布偏向速度较低的一侧。