CELLULAR-AUTOMATA MODEL OF THE ACCRETION DISK

Two-dimensional Boltzmann cellular automaton is introduced to model a thin, stationary accretion disk in a close binary system. The viscosity is modelled in a kinetic fashion through a prescribed algorithm of ''collision processes''. The presence of viscosity is shown to modify the structure of the disk: Keplerian laws for the orbital velocity are modified by factors which depend on the radial distance exponentially. The corresponding coherence length is studied as a function of the viscosity. It can become arbitrarily large for small viscosities. Dynamics of a disk expansion from a ring state are also studied.