氢气泡法图像的数字化处理分析

Digitalization and analysis of hydrogen-bubble visualized flow structures

对氢气泡法产生的时间线进行数字化,把图像的灰度分布存入数组进行运算,识别氢气泡时间线的前缘和后缘。根据距氢气泡发生线最近的两条时间线的前缘或后缘间距以及氢气泡时间线的时间间隔,计算流速分布。本文还提出一种测量湍流结构的速度的方法,简称结构相关法:对两幅一定时间间隔的氢气泡图像进行数字化得到灰度数组,圈定拟序结构的一部分,利用相关原理比较两图像的数组,得到所圈定拟序结构的位移,进而求得其运动速度。

Flow velocity was calculated from hydrogenbubble visualization results with timelines. The pictures were digitalized, and gray distributions were obtained. By calculation, edges of timelines could be identified, then the instantaneous streamwise velocity distribution near the hydrogenbubble generating wire could be calculated from the timeline spacing and the corresponding time interval. Some results about hydrogenbubble visualized flow structures in an artificially excited transitional boundary layer were treated in this way. One better method, called flowstructure correlation, was also presented. From the correlation between two pictures of the same structure, moving speed of a flow structure was obtained. The instantaneous moving velocity, both in streamwise and spanwise directions, of a segment of the leg of a hairpin vortex in the transitional boundary layer was obtained from the digitalized data.