Smoothed particle hydrodynamic simulations of viscous accretion discs around black holes

Abstract

Viscous Keplerian discs become sub-Keplerian close to a black hole since they pass through sonic points before entering into it. We study the time evolution of polytropic viscous accretion discs (both in one and two dimensional flows) using Smoothed Particle Hydrodynamics. We discover that for a large region of the parameter space, when the flow viscosity parameter is less than a critical value, standing shock waves are formed. If the viscosity is very high then the shock disappears. In the intermediate viscosity the disc oscillates very significantly in viscous time-scale. Our simulations indicate that these centrifugally supported high density region close to a black hole plays an active role in the flow dynamics, and consequently, the radiation dynamics.