Translation of two coaxial, nonhomogeneously structured flocs normal to a plate
Journal
Colloid and Polymer Science
Journal Volume
286
Journal Issue
14-15
Pages
1593-1604
Date Issued
2008
Author(s)
Abstract
The translation of two identical, coaxial, nonhomogeneously structured flocs in a Newtonian fluid normal to a plate is analyzed theoretically for the case where the Reynolds number ranges from 0.1 to 40. The geometry considered is capable of simulating the behavior of a floc near a boundary when other flocs may present. The description of the structure of a floc is based on a two-layer model where the permeability of its inner layer can be different from that of its outer layer. We show that the influence of the plate on the flow field near the near floc is more significant than that near the far floc, but the behavior of the corrected drag coefficient of the far floc is more complicated than that of the near floc. In general, the presence of the plate has the effect of raising the drag on a floc. The more nonhomogeneous the floc structure is, the more appreciable the deviation of the corrected drag coefficient-Reynolds number curve from the corresponding Stokes' law-like relation. An empirical relation, which correlates the corrected drag coefficient with the Reynolds number, the separation distance between two flocs, the floc-floc distance, and the ratio permeability of outer layer to permeability of inner layer, is proposed. ? Springer-Verlag 2008.
Subjects
Boundary effect
Drag
Flocs
Nonhomogeneously structured
Sedimentation
Two flocs normal to plate
Type
journal article