Application of a color-coded particle tracking technique to granular flows

This paper implements the color-coded particle tracking velocimeter (CCPTV) to granular flows. In the CCPTV method, grey level is used to encode the temporal information rather than the intensity of particle. Therefore the incoming video signal is processed by an input look-up table in real time. Images in different time can then be superimposed into one frame. Since grey levels now represents images at four different time, there are many values that are not used. We use different threshold grey levels to distinguish different materials in the debris mixture. From the image of a mixture of air, black sand and white sand, information of the particle velocity, phase velocity, and density of debris flows can be obtained. Since density is known to vary with velocity, a method of obtaining density without disturbing the debris flow is very valuable.