N-Particle-Simulations of Dust Growth. I. Growth Driven by Brownian Motion
S. Kempf, S. Pfalzner, T. K. Henning;
Icar, 1999, 141, 388
ABSTRACT:In this paper we investigate the Brownian stage of dust growth in the cold part of a protoplanetary disc around a young stellar object.
The
growth due to diffusive particle motion is simulated numerically by a new
N-particle method.
In contrast to earlier studies the dust growth was
investigated at astrophysically relevant small number densities.
We found that
the friction time of the grains scales with the fifth root of the particle
radius although the average fractal dimension of the growing grains is
smaller than two.
The distribution of fractal dimension is very broad and
about 10% of the dust grains have fractal dimensions larger than
two.
Nevertheless, the determined time scales of the pure Brownian dust growth are much too
large for explaining the formation of planets within the lifetime of a
protoplanetary disc.
Our numerical results indicate that at very low number
densities the Smoluchowski theory is not applicable for the description of the
growth process.
The reason might be that at low number densities spatial
density fluctuations of the dust grains start to strongly influence the growth
process.
PERSOKEY:dust, size distribution, ,
CODE: kempf99