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Investigation and Control of the Combined Three Dimensional Organized Structures in Turbulent Wakes behind Bluff Bodies

断崖体后湍流尾流中组合三维组织结构的研究与控制

基本信息

批准号：
11650193
负责人：
TANAKA Shuji
金额：
$ 2.3万
依托单位：
Toyota Technological Institute
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

The unsteady three dimensional flow structures behind a finite circular cylinder with an aspect ratio of 10 and a thin circular disc at various angles of attack have been investigated. The flow details in the frequency domain were determined using FFT analyzer and the features of large-scaled organized structures in the turbulent wakes were obtained with phase-locked averaging technique in the time domain. Three typical organized structures with different frequencies and different features were extracted from the complex turbulent wake flows. The results can be summarized as follows :1. The wake flows behind a finite circular cylinder typically consist of the following three large-scaled organized vortex structures with different origins, (1) low frequency component(tip component), which is a pair of longitudinal vortices shed from a tip of the cylinder, (2) mid-frequency component (mid-span component), which is hairpin typed organized vortices shed from a mid-span of the cylinder, (3) … More high frequency component (root component), which is shed from the root of the sylinder and quite similar to the two-dimensional Karman's vortices .2. The wake flow behind a finite circular cylinder consists of not only the typical three types of organized vortex structures described above but also various types of vortices with intermediate features and frequencies as well as small eddies with almost random configurations. Therefore, the turbulent wake behind a circular cylinder appears to be a very complicated flow at a glance.3. The wake flow behind a thin circular disc with longituninal vortices, which is a typical vortex features for unstalled conditions, indicates only a few organized structure. The wake flow with ring-type vortices, which is typical vortex features for stalled conditions, indicates a clear organized flow structures with well defined frequency. The Strouhal numbers of the frequency based on the height of the shed ring-type vortices are in the range from 0.19 to 0.22. Less

本文研究了不同攻角下展弦比为10的有限长圆柱和薄圆盘后的非定常三维流场结构。在频域上利用FFT分析仪获得了流动细节，在时域上利用锁相平均技术获得了湍流尾流中大尺度有序结构的特征。从复杂的湍流尾迹流场中提取了三种不同频率、不同特征的典型有组织结构。主要研究结果如下：1.有限长圆柱尾流通常由以下三种不同起源的大尺度有序涡结构组成：（1）低频分量（尖端分量），即从圆柱尖端脱落的一对纵向涡;（2）中频分量（中跨分量），即从圆柱中跨脱落的发夹型有序涡; ...更多信息高频分量（根部分量），从圆柱根部流出，与二维卡门涡十分相似.有限长圆柱后的尾流不仅包括上述三种典型的有组织的涡结构，而且还包括具有中间特征和频率的各种类型的涡以及几乎随机形状的小涡。因此，圆柱后的湍流尾迹流，乍看之下是一个非常复杂的流动.非失速状态下薄圆盘尾流中的长轴涡是典型的旋涡特征，但其结构却很少。尾迹中的环形涡是失速状态下的典型涡特征，表现出明显的有组织的流动结构和明确的频率。基于脱落环型涡高度的频率的Strouhal数在0.19至0.22的范围内。少