FLOW MEASUREMENTS USING VISUALIZED COLOR IMAGES

This paper presents some flow measurement systems based on color image information. The first one is a quantitative thermal flow visualization system to obtain simultaneously both velocity and temperature distributions. Flow visualization is accomplished by the use of thermo-sensitive liquid crystal tracers. A correlation method gives the 2-D velocity vector distribution. An algorithm for the color-to-temperature calibration is presented to obtain the temperature distribution.
The second one is a 3-D flow velocity vector measurement system using tracer images visualized by a color spectrum. In this system, tracer particles are visualized by a color spectrum slit method using a prism. The color of a tracer particle can determine its position in one direction. In the other two directions, the tracer particle can be tracked in consecutive frames of the 2-D tracer image by using a correlation and a particle tracking method. A 3-D velocity vector is consequently obtained by a combination of the color spectrum with the methods for 2-D velocity vector measurement.
The last one is another 3-D flow velocity vector measurement system using a spatio-temporal correlation method. The method needs two tracer particle color images observed at a short distance in the flow direction. Each of the images is a time series. The spatial correlation gives 2-D information on a 3-D velocity vector. In addition, the temporal correlation gives information on the third dimension. A 3-D velocity vector is consequently obtained by calculating the spatio-temporal correlation between the two images.