Brownian dynamics simulation of the aggregation of submicron particles in static gas

• The cluster–cluster aggregation model resulted in a soot-like branching shape.
• Gas temperature affected the shielding effect of the aggregate branch.
• The branching of the aggregate increased with low particle number density.
• The size and aspect ratio of the field affected the aggregation shape.

A Brownian dynamics simulation was conducted to investigate the formation of aggregates that are composed of submicron particles such as soot. Three models were considered for aggregation: a diffusion-limited aggregation model, in which an aggregate grows around a fixed particle; a particle–cluster aggregation model, in which a single aggregate grows by collisions between particles and the aggregate; and a cluster–cluster aggregation (CCA) model, in which many particles and aggregates form multiple aggregates. A comparison of the three aggregation models showed that the CCA model resulted in a soot-like branching shape. The aggregation was investigated by employing the CCA model; it was determined that increase in gas temperature affected the shielding effect of the aggregate branch by changing the displacement and velocity of Brownian particles. Furthermore, these simulations demonstrated that the size and aspect ratio of the field and the particle density also affected aggregation shape.