摘要:
基于图像处理技术,对明渠紊流近壁区的水流低速条带结构进行了测量和分析。条带结构采用天然沙进行示踪,使用高清相机拍摄高分辨率图像,通过形态学方法提取其几何特征。分析条带的宽度及间距的变化特点,得到结果:① 低速条带宽度从水槽中线到两侧壁逐渐变小,沿中线基本呈对称分布;② 摩阻雷诺数在276~465范围时,条带宽度和间距量纲一值的变化范围分别为20.8~29.8和 99.3~126.7,条带面积占图像总面积百分比为23.4%~15.9%;③ 随摩阻雷诺数增大,低速条带的宽度和间距加大,而条带面积百分比逐渐减小。试验结果表明,低速条带结构随水流摩阻雷诺数的变化非常复杂,而图像处理技术提供了一种高效率、高精度的测量手段。
关键词:
-
明渠
/
-
紊流
/
-
低速条带
/
-
图像处理
/
-
摩阻雷诺数
Abstract:
Image-based experiments have been conducted to measure low-speed streaks in the near-bed region of open channel flow. The measurements involve tracing the streaks with natural sand, recording the streak images by a high-resolution camera, and extracting geometrical features of the steaks through mathematical morphology procedure. Analysis of the measured data yields the following findings: ① The streak width is symmetric with respect to the midline of the bed, attaining its maximum value at the center and decreasing gradually toward the side wall; ② At friction Reynolds number from 276 to 465, the low-speed streaks vary from 20.8 to 29.8 in dimensionless width, from 99.3 to 126.7 in dimensionless interval, and from 23.4% to 15.9% in percentage area; and ③ An increase of friction Reynolds number leads to an increase in the width and interval of streaks together with a reduction in the percentage area. The experimental results indicate that image processing technique provides an efficient and accurate tool for investigating complex low-speed streaks in open channel flow.
本站查看
下载:
