Grain growth in turbulent protoplanetary accretion disks
H. Mizuno, W. J. Markiewicz, H. J. Voelk;
AaA, 1988, 195, 183

ABSTRACT:The process of coagulation of dust grains in spatially uniform turbulent gas, where at the low mass end of the grain size spectrum small interstellar grains are assumed to be added continuously, was studied. The turbulence-induced collision velocity between two grains was calculated including a finite inner scale of the turbulence, and the asymptotic mass spectrum and dust opacity were obtained. These calculations were applied to the case of a rotating protostellar nebula, where the central object accretes mass through a turbulent accretion disk, which in turn is fed by material from an extended collapsing outer envelope. It is shown that the grain opacity initially increases with time, keeping the disk convectively turbulent; later on, even though the disk is fed by small particles, convective instability ceases due to the decrease of the opacity on account of grain growth. During the following quiet episode, the freshly added interstellar grains can increase the disk opacity again until convection restarts. It is shown that planetesimal formation might be possible through sedimentation during the laminar phases.
KEYWORDS: accretion disks, cosmic dust, cosmology, particle size distribution, protoplanets, turbulence effects, angular momentum, extrasolar planets, laminar flow, nebulae, planetary evolution, solar system, spectrum analysis
PERSOKEY:turbulence, dust, size distribution, ,
CODE: mizuno88