Particle imaging velocimetry measurement of particle number rate and velocity for falling particles

The number of particles passing through the whole field of interest in a unit lime, referred to as the articles particle number rate, cannot be measured accurately and easily by the conventional methods when the number density of particles is high. However, there are many demands for whole field measurement of the particle number rate in various industrial processes. The purpose of the present investigation is to develop a new method for measuring the particle number rate by introducing PIV (Particle Imaging Velocimetry). In the present work, particles coming out of a hopper, and then falling in air or water were treated. Images of the falling particles were taken by a high speed video camera. Particle velocities were measured by the PIV based on the Binary Image Cross-Correlation Method (BICC), and the particle number rate crossing a plane could be computed from the mean velocity of particles and the number of the particles in the image. The performance of the present method for measuring the particle number rate was evaluated by numerical simulations and experiments. The experimental results showed that the particle number rate of a cloud of particles could be measured with high accuracy by the newly developed methods. The measurement precision of the particle number rate depends on the number of sampling video frames. Several seconds of video frames can yield sufficient precision of the particle number rate. The present research can be applied to on-line measurement of particles in many industrial fields.