Abstract
The suspension of solid spheres in fully developed vertical pipe
flow has been investigated between particle Reynolds numbers of 2
and 10000 and between pipe Reynolds numbers of 25 and 37000 for
sphere to conduit diameter ratios ranging from 0.046 to 0.274.
It was found that the drag coefficient obtained in the present
study was higher than that reported for spheres suspended or
traveling in bounded or unbounded quiescent fluids. The drag
coefficient was found to depend upon the particle Reynolds number
and the sphere to conduit diameter ratio.
The radial position adopted by the spheres was found to be near the
conduit axis at particle Reynolds numbers below 80 but near the
conduit wall at particle Reynolds numbers greater than 200. A
secondary sphere to conduit diameter ratio effect upon radial
position was observed when spheres were suspended near the conduit
wall.
The spheres underwent four distinct modes of motion; the particular
mode adopted was primarily dependent upon the particle Reynolds
number with a secondary dependency upon the sphere to conduit
diameter ratio. Transitions between modes occurred at particle
Reynolds numbers which were approximately the same as values
reported for changes in the wake structure behind spheres.