Visualized Measurements Of The Flow Around Cylinders In The Microchannel

Microscale particle image velocimetry is developed in the traditional PIV technically for the measurement of microscale flow field, it broke through the limitations of the single-point measurement, realized the no contact interference, high precision microfluidic transient velocity field measurementmicrochannel cylinder measurement of the flow field around the preferred experimental means.A new measurement method for3D2C velocity by using Micro-PIV technique under the condition of low density tracer particles is introduced in this study. For the low density tracer particle images, more contribution of background noises and out-of-focus particles to the PIV correlation can generate more significant measurement errors. The high quality images 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. Then high density particle images are obtained by image overlapping to realize the cross-correlation analysis for the two-dimensional velocity field. The3D2C velocity can be constructed with different depths of two-dimensional velocity stacked together by computer technology. The study results indicate that the high density particle images obtained by the method of the particle image overlap which can realize the microfluidic velocity analysis under the condition of low tracer density particles. The constructed three-dimensional velocity can properly reflect the flow characteristics in the microchannel.Then the method of image overlapping is applied to construct the3D2C velocities of three types of the microchannels filled with different arrays of micro cylinders. By comparing with the result of high density, the result of low density further verity the feasibility of the Micro-PIV image overlapping, and the flow field is decided by the structure of the arrays of the cylinders.At last, a preliminary research of the flow around a stubby micro cylinder is processed based on Micro-PIV. The cylinder wake flow of single micro cylinder, in-line arranged double cylinders and side-by-side double cylinders are measured with different Reynolds numbers. A series of problems are launched encountered in the Micro-PIV experiments.