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Structure Analysis and Control of Necklace Vortices Generated between Two Circular Cylinders Forming a Separating Cross

形成分离十字的两个圆柱体之间产生的项链涡流的结构分析与控制

基本信息

批准号：
14550168
负责人：
YAMADA Hidemi
金额：
$ 1.79万
依托单位：
Tokuyama College of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

The three dimensional flow field area and the necklace vortices structure around two cylinders forming a separating cross were visualized using a dye injection method and a tracer particle method under the Reynolds number between 500 and 2000, and the surface pressure distribution on two circular cylinders was measured under the Reynolds number between 1000 and 8000 in detail to clarify the necklace vortex structures in uniform flow and the effects of the necklace vortex behavior on the fluid force into and on the separation flow from the cylinders. In addition, the relationship between the necklace vortex structure being made change by the gap distance and the pressure distribution on the surface of the cylinders was investigated.It is found that the various patterns of the necklace vortices system are produced, depending on the gap distance "G" between two cylinders. In the case of the gap distance ratio "G/d" between 0 and 0.1, the boundary layer on the surface of the upstream cylinder separates and rolls up as a small necklace vortex in the front of the downstream cylinder, and the vortex system with 4 vortices is produced in the symmetrical plane of y/d=0. In the case of G/d=0.2-1.0, a pair of main necklace vortices grows in the gap space between two cylinders, and the 8 vortices system as total is produced. In the case of G/d=1.0-1.5, the pair of main necklace vortices starts vibrating as well as twin vortices behind a cylinder in the low Reynolds number. In the case of G/d=1.5-2.0, the behavior of necklace vortices behind the upstream cylinder is similar to that of Karman vortices under the low Reynolds number.

在雷诺数为500 ~ 2000的条件下，采用染料注射法和示踪粒子法对形成分离交叉的两圆柱周围的三维流场区域和项链涡结构进行了可视化。在雷诺数为1000 ~ 8000的条件下，详细测量了两圆柱的表面压力分布，阐明了均匀流动时的项链涡结构，以及项链涡行为对进入和离开圆柱的流体力的影响。此外，还研究了间隙距离变化所形成的项链涡结构与气缸表面压力分布的关系。研究发现，根据两圆柱间隙距离“G”的不同，会产生不同的项链涡系统图案。当间隙距离比G/d在0 ~ 0.1之间时，上游筒体表面的边界层在下游筒体前方分离卷起，形成一个小项链涡，在y/d=0的对称平面内形成4个涡的涡系。当G/d=0.2-1.0时，在两缸间隙中产生一对主项链涡，共形成8个涡系。G/d=1.0-1.5时，低雷诺数下一对主项链涡开始振动，圆柱后双涡也开始振动。当G/d=1.5 ~ 2.0时，上游柱体后的项链涡的行为与低雷诺数下的卡门涡相似。