Two-Dimensional Digital Particle Tracking Velocimetry Algorithm Based on the Image of Particle Trace

Abstract

A digital method is developed to judge the instantaneous flow velocity by the image of the moving tracer particle formed during the exposure time. The grey-scale image of the particle trace is changed into the binary image and the pixels included in the particle trace image are marked. The length of the particle trace is obtained by determining the central principal axis of the particle trace image. The direction of the particle moving is determined by the fact that the flow velocities in a small local domain are almost the same. The instantaneous flow velocity field in the channel is measured by the method presented in this paper. The mean flow velocities along the vertical direction obtained by averaging the instantaneous velocities agree well with the logarithmic law.