粒子图像速度粒度同场测量基础与实验验证

Fundamentals of particle velocity and size measurement in same field and its experimental validation

从米氏散射理论(Mie scattering)出发,在粒子图像测速法硬件系统结构模型和电荷耦合器件光电转换一般特性基础上,推导出了真实球形粒子在数字相机上所成粒子像各像素点灰度总和的理论计算式。为验证该理论计算式的正确性,采用不同粒径的4种标准粒子进行实验,考察粒子像点灰度和随粒子曝光时间、照明用激光脉冲光强及真实粒子粒径的变化情况。结果表明:粒子像点灰度和随曝光时间及激光光强的变化呈线性趋势,基本与理论推导结果相一致。相同实验条件下的不同粒径标准粒子所成像点灰度和比值均在粒子粒径平方比附近,符合理论结果。

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.