径移主导吸积盘的含时数值模拟

The Time Dependent Numerical Simulation of Advection-Dominated Accretion Flow Disk

黑洞吸积被认为是活动星系核的能量来源,而研究黑洞吸积最主要的难题是要解释吸积气体的角动量是如何转移出去的。黑洞吸积盘理论提出通过粘滞力矩转移角动量。径移主导吸积盘模型(advection-dominated accretion flow,简称ADAF)是几何厚、光学薄的低吸积率吸积盘模型,它在解释低光度活动星系核的一些观测现象时获得了很大的成功。近年来,随着计算机技术的迅猛发展,数值模拟在天体物理研究中获得了广泛的应用,也取得了突破性的进展。主要工作是用数值模拟方法研究ADAF整体解作为初始条件模拟黑洞的吸积过程。

Accretion onto the black hole is believed to be the central engine of active galactic nuclei （AGN）. The main obstacle to accretion of gas onto black hole is large specific angular momentum. The most famous accretion solution is the geometrically thin and optically thick cold disk model de- veloped by Shakura and Sunyaev （1973）. This solution presents standard ＇c~ viscosity ＇ to transport angular momentum. But it cannot explain the low-luminosity AGNs. Narayan and his collaborators present the geometrically thick and optically thin hot disk model -- advection dominated accretion flow （ADAF）. The low-luminosity AGNs and black hole X-ray binaries can be explained well by the ADAF model. The numerical simulations of ADAF have achieved a lot of progress in recent years. One is the convective instability in ADAF model, therefore only a fraction of the accretion material available at the outer boundary is actually accreted onto the central black hole and also changes the structure of the accretion flow. We report on our study of accretion flows onto black hole by means of numerical, axisymmetric, hydrodynamical simulations in two-dimension. We consider the accretion flow with different initial conditions. The angular momentum of the flow is transported by the viscosity stress tensor. Our main result is that the properties of the accretion flow depend on the initial conditions. The flow with low angular momentum can accrete more material than that with high angular momentum. So the initial conditions play an important role on the structure of accretion flow.