||Numerical Viscosity Effects and Turbulent Properties of the ICM in SPH Simulations of Galaxy Clusters
||453, Advances in Computational Astrophysics: Methods, Tools, and Outcome
||A SPH code employing a time-dependent artificial viscosity scheme is
presented in which each particle has its own viscosity parameter, whose
time evolution is governed by the local shock conditions.
The new SPH code is then used to construct a large set of
N-body/SPH hydrodynamical cluster simulations. These simulations are aimed at
studying in SPH simulations the impact of numerical viscosity
and the development of turbulence in the ICM of the simulated clusters.
To this end spectral properties of the gas velocity field are investigated at
the present epoch by measuring for the simulated clusters the velocity power
spectrum E(k). Dissipative effects are found to be significant at length
with viscous damping of the velocities being less pronounced in those runs with
the lowest artificial viscosity.
The turbulent energy density radial profile Eturb(r) is strongly affected
by the numerical viscosity scheme adopted in the simulations, with the
turbulent-to-total energy density ratios being higher in the runs with the
lowest artificial viscosity settings and lying in the range between a few
percent and 10%. These values are in accord with the corresponding ratios
extracted from previous cluster simulations realized using mesh-based codes.
Finally, radiative runs are characterized by the presence in the cluster inner
regions of high levels of turbulence, generated by the interaction of the
compact cool gas core with the ambient medium.