(347b) Dispersion of Aggregates in Shear Flow

A novel development of the Accelerated Stokesian Dynamics method presented in this paper includes the aggregation and breakage in suspensions of varying stability. This method has been used to calculate the necessary forces needed to break aggregates in shear flows.

The methodology of the aggregate breakage is investigated using two and three particles arranged in a vertical manner, sticking to each other as a result of the interparticle forces (DLVO-theory). Due to additional velocity gradients, movement of the other particles is governed by the resultant forces acting on them. Additionally, the breakup of fractal aggregates free to move with the fluid has been investigated. It could be shown that the aggregate breaks up at once if the shear is high enough even if the aggregate is free to move. The resulting fragments break into other smaller parts which can aggregate and break up again. Dense clusters or clusters with bone-like forms are most stable.

Furthermore, randomly distributed anisotropic model aggregates consisting of spherical particles arranged as small rods in a fluid are exposed to shear flow. The structure changes due to aggregation and breakup depending upon the boundary conditions. Here, structural development will be discussed for two parameters: interparticle and shear forces. The resulting network structure is analyzed in terms of porosity profiles, pair correlation function and average coordination number.