标题: | 彩色质点影像测速法于瞬间溃坝流场之试验研究 Experimental Study on Instantaneous Dam-Break Flows Using Color Particle Image Velocimetry Method |
作者: | 杨升学 Sheng-Hsueh Yang 叶克家 Keh-Chia Yeh 土木工程学系 |
关键字: | 彩色质点影像测素法;瞬间溃坝;color particle image velocimetry (CPIV);instantaneous dam-break |
公开日期: | 2001 |
摘要: | 本文旨在利用CPIV法进行流场可视化之研究,系利用雷射光及多彩声光调变器(PCAOM)将雷色光束区分为蓝绿两光束形成二维雷射光页,再利用彩色数位相机(Color CCD)之技术所组合成。在流体中加入与水相近密度之显影塑胶颗粒(1.1 g/cm3),在蓝绿相间隔之雷射光页下显影其流场变化,并撷取流场变化之数位影像。再将所撷取之数位影像讯号,进行数位相关法分析求得位移量,再除以曝光时间间距而得知速度值。 其CPIV方法之准确性分析系利用定速转盘验证之,于已知转盘速度下进行影像撷取、影像分析与数为相关计算,求得之速度值再进行比对,作为试验计算之验证对照组。随后进行光滑及糙度底床试验之瞬间流场之研究,因床质材料糙度增加,造成流场于近底床附近有明显地变化,形成涡流现象。最后应用于瞬间溃坝后流场流况作分析,将瞬间溃霸所形成之变量流利用摄影机拍摄,并分析其水位随时间之变化情形、及动床底床因瞬间溃决后下游底床利用描绘方式记录床形变化,及利用CPIV法将所设定之不同渠段之流场,透过数位影像及运算程式进行可视化分析研究 。 The purpose of this study is to investigate flow field visualization by using the color particle image velocimetry (CPIV) method. This method uses the laser light, polychromatic acousto-optic modulator (PCAOM) which separates the laser beam into blue and green color light sheets, and digital color charge coupled device (CCD). Polystyrene of diameter 75μm and density 1.1 g/cm3 is used as the seeding material. The obtained digital image is first transferred into digital signal data, and then the displacement of the seeding particles is estimated by the cross correlation analysis. The corresponding velocity of the particle is equal to the displacement divided by the exposure time interval. To velocity the accuracy of the CPIV method, the experiment on the stability rotating disc is executed. The computed rotating velocity is compared with the known rotating velocity and the relative error is acceptable. Then, the CPIV method is applied to study the flow fields for smooth and rough channel beds. Irregular eddy zones occur due to the existence of the rough bed. Finally, the CPIV method associated with the video camera is applied to study the flow field of instantaneous dam-break case. The variations of water surface and bed surface are recorded by the video camera. In the same time, flow field visualization of propagation of the model dam-break wave is by the CPIV method. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#NT900015078 http://hdl.handle.net/11536/68119 |
显示于类别: | Thesis |