三维粒子示踪测速技术的开发及初步应用

开发的单颗粒三维运动轨迹测量系统的硬件由四部摄像机、一台PC机和内置的图像卡组成。软件系统包括4路图像实时同步采集、图像二值化和聚合程序，坐标校正和转换，以及各统计参数的计算公式。系统标定的空间误差小于0.3mm，速度误差约为1.0mm/s。开发的颗粒三维运动测量系统在测量颗粒运动更长的轨迹、实现较高的采样频率和保证每个摄像机的高分辨率、只进行一次标定而进行各种水力坡度的试验及实现极大样本的采集等方面都取得了明显的进展，为研究颗粒运动的基本规律提供了新的方法。试验可以得出颗粒三维运动的瞬时速度，初步试验得出颗粒的纵向平均速度遵循对数分布，颗粒速度小于相应水流的运动速度。

The development and elementary application of 3-D partricle tracking velocimetry

A new Particle Tracking Velocimetry(PTV) measuring system was developed to investigate the 3-D trajectory of single particles in a steady open channel flow.It consists of four cameras,which are connected to a PC via a PCI Image Board.The system actualizes the synchronous video sampling of these four cameras in real time.By transforming the captured pictures into binary pictures,it gives the locations of the particles in pixel coordinates.After calibration,the particle space coordinates are determined.These results are used to reconstruct 3-D trajectories of the particles and calculate the velocity field.The space error of 3-D PTV system is less than 0.3mm and the velocity error is about 1.0mm/s.The system offers a wide measuring volume,a high sampling frequency and a high image resolution.It is possible to obtain large amounts of samples.These advantages make the system a new way to research the particle motions.The results of preliminary experiments show that the distribution of stream-wise particle velocity follows the log-law,and the particle velocity is lower than the corresponding clean water flow.