The standard ballistic aggregation model assumes that the particles th
at are added to a growing agglomerate follow straight-line trajectorie
s. The finite viscosity of real fluids, however, biases the flow of li
quid around, rather than through, the agglomerate. The result is that
the particles, which follow streamlines in the fluid, will tend to be
deposited near the periphery of the growing agglomerate. A modificatio
n is made to the ballistic aggregation model to account for this effec
t, and the geometry of the resultant structures is characterized, The
simulation results suggest that even under conditions where convection
dominates particle motion, branched open structures are likely to be
formed. (C) 1995 Academic Press, Inc.