We investigate the effects of various ways of injection of gas at the outer boundary in the numerical simulations of non-viscous accretion flows.We study three models.In Model A,we inject material around the equatorial plane.In Models B and C,fullrange θ injection is used(we employ spherical coordinates).In all three models,the injected material has the same density distribution with polar angle θ.From the equatorial region to the polar regions,angular momentum of the injected material of Model B decreases faster than that in Model C.For all of the models,after a transient episode of infall at the beginning of the simulations,the gas piles up in the equatorial regions outside the black hole and forms a thick torus bounded by a centrifugal barrier.We find that the accretion rates of Models B and C are more than ten times higher than that in Model A.In Model A,there is weak accretion only in the torus and outflows are found on the surface of the torus.In Model B,we find strong inflows on the surface of its torus,and the accretion in the torus is weak.In Model C,strong inflows also occur on the surface of its torus,but the accretion regions are narrower and there are strong outflows in its torus.In all of our models,the time-averaged density,pressure and angular momentum in the equatorial region can be described by a radial power law,with P ∝r-3/2,P ∝r-2 and l∝r0.
BU DeFu,YUAN Feng,WU MaoChun & YANG XiaoHong Key Laboratory for Research in Galaxies and Cosmology,Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China
We report on the effects of isotropic thermal conduction in non-radiative collisionless accretion flows in two dimensions.In comparison to accretion flows without conduction,we find that the disk generally becomes cooler and thinner.Specifically,the magnitude of this effect depends on the kinetic viscosity coefficient.If it is proportional to density,the density profile of the accretion flow is flat,therefore the effect is not very obvious.But,if it is proportional to r1/2,as is usual for the "α" disk description,the density profile is steeper.Therefore,the effect will be much more obvious,with the temperature profile of the accretion flow becoming much flatter.This will have important observational consequences.
WU MaoChun,YUAN Feng & BU DeFu Key Laboratory for Research in Galaxies and Cosmology,Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China
The hot accretion flow model was re-discovered in 1994 by Narayan and collaborators.Intensive theoretical works have been conducted and significant progresses have been achieved.In this paper,we review several developments in the past ten years.This mainly includes the finding of outflow and convection and its dynamical effect on inflow;the direct electron heating by viscous dissipation;the effect of large scale toroidal magnetic fields in the inner region of the accretion flow;and the effect of global Compton scattering.Their observational applications are also introduced very briefly.
YUAN Feng Key Laboratory for Research in Galaxies and Cosmology,Shanghai Astronomical Observatory,Chinese Academy of Sciences,Shanghai 200030,China
