Viscous damping in self-gravitating accretion discs

A two-dimensional numerical hydrodynamics code is developed to model viscous accretion discs, employing the method of smoothed particle hydrodynamics. The effective shear viscosity present in the code is evaluated and used to model a physical shear viscosity. Using a polytropic equation of state, models of self-gravitating accretion discs are evolved with a range of physical parameters, including viscosity. From these models it is found that a characteristic mass accretion rate, constant with time, tends to be maintained by accretion discs, and that mass accretion is inversely proportional to the strength of the effective shear viscosity. This is a consequence of the damping effect of local viscous forces upon the global non-axisymmetric modes that primarily drive accretion in these discs. In addition, the formation of satellites (self-gravitating clumps) is observed in models which also develop a dominating m=1 mode. The possible relevance of these satellites to planet formation is discussed.