SELF-PRESERVING SIZE DISTRIBUTIONS OF AGGLOMERATES

The attainment of self-preserving distributions by coagulation of aggl omerate or aggregate particles has been investigated in the continuum and free-molecular regimes. Self-preserving distributions have been co mputed for agglomerates of various fractal dimensions. In the free-mol ecular regime, the self-preserving size distributions broaden as the f ractal dimension decreases. In contrast, in the continuum regime, the distributions narrow with decreasing fractal dimension. The aggregate growth rate increases with decreasing fractal dimension of the collidi ng particles. This effect is more pronounced in the free-molecular tha n in the continuum regime. In the free-molecular regime, particles of low fractal dimension have larger cross-sectional area than particles of equal mass but with higher fractal dimension. The larger cross-sect ional area per unit particle mass results in a direct increase in the coagulation rate. In the continuum regime, the effect of enhanced coll ision area is reduced by the increased drag of the agglomerates.