TASK Quarterly (Jul 2001)
DISPERSION OF COLLOIDAL AGGLOMERATE IN MESOSCALE MODELLED BY A HYBRID FLUID PARTICLE MODEL
Abstract
The dispersion of the agglomerating fluid process involving colloids has been investigated at the mesoscale level by a discrete particle approach – the hybrid fluid particle model (FPM). Dynamical processes occurring in the granulation of colloidal agglomerate in solvents are severely influenced by coupling between the dispersed microstructures and the global flow. On the mesoscale this coupling is further exacerbated by thermal fluctuations, particle-particle interactions between colloidal beds and hydrodynamic interactions between colloidal beds and the solvent. Using the method of FPM, we have tackled the problem of dispersion of a colloidal slab being accelerated in a long box filled with a fluid. Our results show that the average size of the agglomerated fragments decrease with increasing shearing rate Γ, according to the power-law A·Γk, where k is around 2. For larger values of Γ, the mean size of the agglomerate Savg increases slowly with 0 from the collisions between the aggregates and the longitudinal stretching induced by the flow. The proportionality constant A increases exponentially with the scaling factor of the attractive forces acting between the colloidal particles. The value of A shows a rather weak dependence on the solvent viscosity. However, A increases proportionally with the scaling factor of the colloid-solvent dissipative interactions. These results may be applied to enhance our understanding concerning the nonlinear complex interaction occurring in mesoscopic flows such as blood flow in small vessels.
