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Supermassive black holes are probably present in the centre of the majorityof the galaxies. There is a consensus that these exotic objects are formed bythe growth of seeds either by accreting mass from a circumnuclear disk and/orby coalescences during merger episodes.  The mass fraction of the disk captured by the central object and the relatedtimescale are still open questions, as well as how these quantities depend onparameters like the initial mass of the disk or the seed or on the angularmomentum transport mechanism. This paper is addressed to these particularaspects of the accretion disk evolution and of the growth of seeds.  The time-dependent hydrodynamic equations were solved numerically for anaxi-symmetric disk in which the gravitational potential includes contributionsboth from the central object and from the disk itself. The numerical code isbased on a Eulerian formalism, using a finite difference method ofsecond-order, according to the Van Leer upwind algorithm on a staggered mesh.  The present simulations indicate that seeds capture about a half of theinitial disk mass, a result weakly dependent on model parameters. Thetimescales required for accreting 50% of the disk mass are in the range 130-540Myr, depending on the adopted parameters. These timescales permit to explainthe presence of bright quasars at z ~ 6.5. Moreover, at the end of the diskevolution, a "torus-like" geometry develops, offering a natural explanation forthe presence of these structures in the central regions of AGNs, representingan additional support to the unified model.

The growth of supermassive black holes fed by accretion disks