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Development of the measuring technique for local wall shear stress by laser gradient meter

激光梯度仪局部壁面剪应力测量技术的研制

基本信息

批准号：
07555382
负责人：
MASUDA Shigeaki
金额：
$ 2.5万
依托单位：
Keio University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07555382/
关键词：
Wall shear stress Laser gradient meter Optical measurement Turbulent flow Optical fiber wall shear stress laser gradient meter optical measurement turbulent flow

项目摘要

The optical technique for measuring the local wall shear stress has been developed. At the first year of the project, the feasibility study of the method has been conducted by performing the measurement in a two-dimensional channel flow for which a number of experiments in the past to be referred as well as DNS database are available. The measurements of turbulence statistics have been undertaken under the varying Reynolds number.The test rig is a plane channel with the channel aspect ratio of 1 : 32 and 2m long. The width of the channel H is 20mm, and the measurements have been conducted at the location 160H distant from the channel inlet. The obtained mean skin friction coeffecient has well been corrilated with the existing experiments and DNS within 1%. The good agreements have been obtained also for the turbulence statistics such as the second-moment, skewness as well as the flatness factors.In the second and third year of the project, the effort has been paid for the development of the transmitting optics system that makes use of an optical fiber joint to improve the flexibility of the system. Because the precise manipulation of the thin fiber has required an extreme skill for preparing the suitable fiber arrangement, requiring the adjustment of the distance between two parallel flber core to be 20mum, most of the period has been used to develop the fiber joint mechanism. However, the therefrom achieved system has been proven to be more stable and reliable compared to the original system.It has also been discussed on the possibility of the use of analogue sensor that enables the detection of valid signal which may otherwise be rejected during the data validation algorithm in the statistic process. A V-type hot-wire sensor, mounted in a small hole on the wall, has found to be a potential candidate for the pilot analogue sensor system.

发展了测量局部壁面切应力的光学技术。在该项目的第一年，该方法的可行性研究已经进行了二维通道流的测量，在过去的一些实验中被引用，以及DNS数据库是可用的。实验台是一个长宽比为1：32、长2m的平面通道，在不同雷诺数下进行了湍流统计特性的测量。通道H的宽度为20mm，并且在距离通道入口160H的位置处进行测量。所得的平均摩阻系数与已有的试验结果和DNS值的相关性在1%以内。在第二年和第三年的研究工作中，我们致力于发展一种利用光纤接头的传输光学系统，以提高系统的灵活性。由于细纤维的精确操作需要极端的技能来准备合适的纤维布置，需要将两个平行纤维芯之间的距离调整为20 μ m，因此大部分时间用于开发纤维连接机构。然而，由此实现的系统已被证明是更稳定和可靠的相比，原来的system.It还讨论了使用模拟传感器，使有效的信号，否则可能会被拒绝在数据验证算法在统计过程中的检测的可能性。一个V型热线传感器，安装在墙上的一个小孔，已被发现是一个潜在的候选人的试点模拟传感器系统。