Abstract

We study the hydrodynamics of steady state viscous, axisymmetric, transonic accretion flows around a Schwarzschild black hole. We adopt a viscosity parameter, α (described by Shakura & Sunyaev, 1973) and compute the highest possible value of the viscosity parameter for each pair of two inner boundary parameters (namely, specific angular momentum l_in at the horizon and specific energy of the flow E(x_in) at the location of the inner sonic point x_in, which is still capable of producing a standing shock. We find that while shocks can still form for the value of α as high as 0.3 in smaller regions of the flow parameter space, its typical value appears to be about 0.01-0.15 which is also the typical viscosity parameters achieved by magnetorotational instabilities in accretion flows.