Measurements of velocity fluctuations in a granular flow

The present work describes a new experimental technique to measure the longitudinal and transverse velocity components in a granular material flow. The technique calculates the velocities by autocorrelating successive digitized images of the flow. The method is applied to flow in a two-dimensional vertical channel. The measurements of the average velocity distribution agree with results from a previous study using a different technique. The velocity fluctuations in the flow direction are approximately 40% of the average velocity. The transverse fluctuations, which have not been previously measured, increase significantly near the walls, and are non-zero in the center of the channel.