Nedderman's method is used and developed to measure particle velocity insid
e a conical hopper by placing a mass of host particles, which dyed a differ
ent color, into an initially static bed. The velocities of glass beads and
sand particles of different sizes were measured in a steel hopper and a Per
spex hopper. The effect of wall friction on the solids flow was also invest
igated by increasing wall roughness with sandpaper stuck on the inside hopp
er wall. (C) 1999 Elsevier Science Ltd. All rights reserved.