TRACKING THE TRANSLATIONAL AND ROTATIONAL MOTION OF GRANULAR PARTICLES - USE OF HIGH-SPEED PHOTOGRAPHY AND IMAGE-PROCESSING

Digital high-speed photography has been used to investigate the dynami cs of a two-dimensional model granular system, consisting of steel or [poly(methyl methacrylate)] discs under vibration between glass walls. Images are analysed by computer using Hough transform algorithms to m easure the two-dimensional position and angle of discs within the fiel d of view. Two preliminary test problems indicate position errors of 5 % to 30% of the pixel separation, and angular errors of 0.017 to 0.025 rad depending on magnification. The combination of all-digital record ing system and automated pattern recognition software allows rapid acq uistion of high quality data. Translational and rotational velocities, calculated for the vibrated discs, are used to construct speed and ve locity distribution functions; the speed distribution closely approxim ates to the Maxwell-Boltzmann distribution and the velocity distributi on is Maxwellian. Granular temperatures are anisotropic over the range of amplitude and frequency of the vibration studied.