SMOOTHED PARTICLE HYDRODYNAMIC SIMULATIONS OF VISCOUS ACCRETION DISCSAROUND BLACK-HOLES

Viscous Keplerian discs become sub-Keplerian close to a black hole sin ce they pass through sonic points before entering into it. We study th e time evolution of polytropic viscous accretion discs (both in one- a nd two-dimensional flows) using smoothed particle hydrodynamics. We di scover that for a large region of the parameter space spanned by energ y, angular momentum and polytropic index, when the flow viscosity para meter is less than a critical value, standing shock waves are formed. If the viscosity is very high then the shock wave disappears. In the i ntermediate viscosity, the disc oscillates very significantly in the v iscous time-scale. Our simulations indicate that these centrifugally s upported high density regions close to a black hole play an active rol e in the flow dynamics, and consequently, the radiation dynamics.