Adding active particles for overall aggregation in a mixing tank: A computational study

In order to achieve flocculation in a dense agitate d solid-liquid suspension of non-aggregating partic les, we explore scenarios where we add a limited amount of aggregative (i.e. active) particles that can bind t he nonaggregative particles. The performance of this proc ess hinges on the competition between mixing – spre ading the active particles over the flow volume – and agg re ation among the active particles, with the latte r reducing their effectiveness. The research has been conducte d in a computational manner: direct simulations of transitional flow in a mixing tank (at an impellerbased Reynolds number of 4,000) are two-way coupled with the dynamics of a collection of spherical, equally sized particles that are given specific aggregativ e properties. The overall solids volume fraction is 10%. A small fraction of all solid particles (5.8%) is active. A ggregation is quantified by means of the average coordination number as well as the aggregate size distribution. The way the active particles are released in the tank volum e has significant effect on the overall levels of a ggregation, specifically for active particles with a strong agg re ative force.