An improved PTV technique to evaluate the velocity field of non-spherical particles

Abstract

In recent years, Particle Tracking Velocimetry (PTV) has been extensively used to measure the translational velocity field of granular assemblies in applications such as vibrated beds, rotating drums and Couette shear cells. However, this technique has not yet been shown to be able to determine the velocity field of non-spherical particles. The aim of this paper is to develop an improved PTV technique to determine translational and rotational velocities for non-spherical particles. To prove the feasibility of this new PTV technique, it was employed to investigate the convection behaviour of non-spherical particles in a vibrated bed. In the demonstration example, paired POM particles made by gluing two single POM beads were studied. The test example was a single layer quasi-2D model. The transport properties of the paired POM particles in a vibrated bed, such as local average velocities, local fluctuation velocities, granular temperatures, fluctuation velocity distributions, self-diffusion coefficients and dimensionless convection flow rates, were evaluated from the experimental results and discussed. The developed improved PTV technique is shown to have the ability to measure more accurately the velocity field of non-spherical particulate systems. The study has demonstrated the convection phenomenon of non-spherical particles in a vibrated bed and has shown that particle rotation is significant in the vibrated granular bed. In such a granular system with convection phenomenon, the average rotational kinetic energy constitutes approximately 5.4% of the average kinetic energy and in some local regions the rotational granular temperature amounts to over 17% of the total granular temperature.