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A black hole accretion is necessarily transonic. In presence of sufficientlyhigh viscosity and cooling effects, a low-angular momentum transonic flow canbecome a standard Keplerian disc except close to the where hole where it mustpass through the inner sonic point. However, if the viscosity is not higheverywhere and cooling is not efficient everywhere, the flow cannot completelybecome a Keplerian disc. In this paper, we show results of rigorous numericalsimulations of a transonic flow having vertically varying viscosity parameter(being highest on the equatorial plane) and optical depth dependent coolingprocesses to show that the flow indeed segregates into two distinct componentsas it approaches a black hole. The component on the equatorial plane hasproperties of a standard Keplerian disc, though the flow is not truncated atthe inner- most stable circular orbit. This component extends till the horizonas a sub-Keplerian flow. This standard disc is found to be surrounded by a hot,low angular momentum component forming a centrifugal barrier dominatedoscillating shock wave, consistent with the Chakrabarti-Titarchuk two componentadvective flow configuration.

Segregation of a Keplerian disc and sub-Keplerian halo from a Transonic flow around a Black Hole by Viscosity and Cooling processes