  High resolution observations with the NIR adaptive optics integral field
spectrograph SINFONI at the VLT proved the existence of massive and young
nuclear star clusters in the centres of a sample of Seyfert galaxies. With the
help of three-dimensional high resolution hydrodynamical simulations with the
Pluto code, we follow the evolution of such clusters, focusing on stellar mass
loss. This leads to clumpy or filamentary inflow of gas on large scales (tens
of parsec), whereas a turbulent and very dense disc builds up on the parsec
scale. In order to capture the relevant physics in the inner region, we treat
this disc separately by viscously evolving the radial surface density
distribution. This enables us to link the tens of parsec scale region
(accessible via SINFONI observations) to the (sub-)parsec scale region
(observable with the MIDI instrument and via water maser emission). In this
work, we concentrate on the effects of a parametrised turbulent viscosity to
generate angular momentum and mass transfer in the disc and additionally take
star formation into account. Input parameters are constrained by observations
of the nearby Seyfert 2 galaxy NGC 1068. At the current age of its nuclear
starburst of 250 Myr, our simulations yield disc sizes of the order of 0.8 to
0.9 pc, gas masses of 1.0e6 solar masses and mass transfer rates of 0.025 solar
masses per year through the inner rim of the disc. This shows that our large
scale torus model is able to approximately account for the disc size as
inferred from interferometric observations in the mid-infrared and compares
well to the extent and mass of a rotating disc structure as inferred from water
maser observations. Several other observational constraints are discussed as
well.
