VELOCITYOF A SINGLEGAS PLUG R1S1NG THROUGHSTAGNANT LIQUID IN A PIPE WITH FALLINGPARTICLES

摘要

Velocities of a single air plug rising through a stagnant water column with falling particles were measured at atmospheric pressure and room temperature. The particles used were glass beads with a diameter of 0.59, 1.02 and 2.08 mm and stainless steel balls of 1.58 and 2.38 mm in diameter, respectively. A transparent Plexiglas pipe of 30.0 mm ID and 4m long was used as the test pipe. The rising velocities of the plug with the falling particles were faster than those without the particles and became faster with an increase in the volumetric flux of the falling particles. A wake region behind the plug was prolonged in the with-falling-particle case compared with that in the without-falling-particle case. The film thickness around the plug became thicker as the volumetric flux of the falling particles were increased. It was suspected that a downward water velocity at the peripheral region along the pipe wall behind the plug was increased by the particles. To compensate it, the upward velocity of water at the central region behind the plug was increased and the rising velocity of the plug became fast.