Abstract:

Based on the structure model of the hardware system of particle image velocimetry and general characteristic of optoelectronic transform of the charge coupled deveice(CCD), a theoretical equation to calculate the sum of the gray levels of the pixels of a real spherical particle image captured by CCD camera was derived from the Mie's scattering theory. To validate the derived equation, the relationships of the particle image gray level with the exposure time, laser light intensity and particle size were investigated employing 4 kinds of standard particle with different sizes. The results show that there is roughly linear relationships existing between particle image gray level and both exposure time and laser light intensity, and the image gray level ratio of 2 standard particles with different sizes is near the ratio of the size square of particles. All the experimental results are in good agreement with those from the derived theoretical equation.

Key words: optics, velocity and size measurement, image gray level, particle image velocimetry