基于低密度粒子图像叠加的Micro-PIV速度场测量

提出了一种基于低密度粒子图像的微流体粒子图像全场测速技术。经过背景噪声去除、阈值过滤、图像增强等图像预处理过程，获得了高质量的低密度荧光示踪粒子图像。对100对图像进行图像叠加处理，得到了满足互相关算法求解二维速度场的高密度叠加粒子图像。针对宽度为250μm，深60μm的长直微通道开展了覆盖全场不同流体层平面的二维速度测量，并利用多个流体平面的二维速度场实现了微通道内全场速度的构建。研究结果表明：由于图像叠加法去除了像径大但灰度低的背景粒子图像，采用互相关分析能够准确获得分层二维速度场，所构建的全场速度场正确反映了长直微通道内流流场特征。

Measurement of velocity by micro-PIV technique based on overlap of low density particle images

A new measurement method for full der the condition of low density tracer particles is field velocity by using micro-PIV technique un introduced in this study. The high quality ima ges of low density tracer particle are approached by the image processes including the removing of background noise, filtering under the threshold of gray scale and the image amplification. 100 pairs of the low density tracer particle images are overlapped, and two frames of the high density particle images are obtained to realize the cross-correlation analysis for the two-dimensional veloc- ity field. Two-dimensional velocities on the different fluid planes along the out-of-plane direction are gained in a long straight microchannel with the cross section of 250μm width and 60μm depth. Hence, the full velocity field inside the microchannel ities on muhi-planes. The study results indicate that is constructed by the two-dimensional veloc- as the background particle images with large image diameter and low grayscales have been removed by the particle image overlap, more accu- rate two-dimensional velocities on different fluid planes can be evaluated by cross-correlation anal- ysis. The constructed full velocity field can properly reflect the flow characteristics of flow in long straight microchannel.