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Paper: Numerical Viscosity Effects and Turbulent Properties of the ICM in SPH Simulations of Galaxy Clusters
Volume: 453, Advances in Computational Astrophysics: Methods, Tools, and Outcome
Page: 405
Authors: Valdarnini, R.
Abstract: 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 scales 100–300Kpc, 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.
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