Pages 67-74
An measurement technique by means of statistical analysis of visualized images have been developed by the authors. The technique is based on the fact that the probability of the particle passing is proportional to the flow speed if the particle concentration is uniform through the measurement area. In the present, the governing equation for the measurement is formed using Lagrange's differentiation. The process of forming the equation is similar to it of the so-called spatio-temporal derivative method. The stream-line coordinate system has been introduced on it in order to obtain the general form so as to apply this technique to the flow field where the particle concentration is not uniform. The new governing equation gives also an idea to measure the velocity component. The image temporal derivative gives the velocity component normal to the particle edge. Therefore the velocity vectors can be obtained through the ensemble average of the product of temporal and spatial derivatives. The principles of the measurement is explained in the case of both one-and two-dimension. The result of a numerical simulation in two-dimensional case shows that the time-mean velocity vector can be obtained directory from the visualized image data.
