基于形心主轴的二维DPTV算法

提出了一种根据曝光时间内示踪粒子形成的轨迹图像来确定瞬时流速的数字化方法.将采集到的粒子轨迹灰度图像转化为二值化图像, 对粒子轨迹图像包含的像素点进行了标记.通过确定粒子轨迹图像的形心主轴得到了粒子轨迹长度,根据流场局部区域运动速度基本相同的事实确定了示踪粒子的运动方向,得到了流体的运动速度.应用本文提出的测速算法对槽道流动的瞬时流场进行了测量.对瞬时测量结果进行平均得到的垂向平均流速分布规律与公认的对数率分布规律相吻合.

Two-dimensional DPTV algorithm based on central principal axis

A digital method is developed to judge the instantaneous flow velocity by the image of the moving tracer particle formed during the exposure time.The grey-scale image of the particle orbit is changed into the binary image and the pixels included in the particle orbit image are marked.The length of the particle orbit is obtained by determining the central principal axis of the particle orbit image.The direction of the particle motion is determined by the fact that the flow velocities in a local small domain are almost the same,and the flow velocity is obtained.The instantaneous velocity field in the channel is measured by the method.The mean flow velocities along the vertical direction obtained by averaging the instantaneous velocities agree with the well known logarithmic law.