Influence of adaptive mesh refinement and the hydro solver on shearinduced mass stripping in a minormerger scenario
Abstract
We compare two different codes for simulations of cosmological structure formation to investigate the sensitivity of hydrodynamical instabilities to numerics, in particular, the hydro solver and the application of adaptive mesh refinement (AMR). As a simple test problem, we consider an initially spherical gas cloud in a wind, which is an idealized model for the merger of a subcluster or galaxy with a big cluster. Based on an entropy criterion, we calculate the mass stripping from the subcluster as a function of time. Moreover, the turbulent velocity field is analyzed with a multiscale filtering technique. We find remarkable differences between the commonly used PPM solver with directional splitting in the ENZO code and an unsplit variant of PPM in the NYX code, which demonstrates that different codes can converge to systematically different solutions even when using uniform grids. For the test case of an unbound cloud, AMR simulations reproduce uniformgrid results for the mass stripping quite well, although the flow realizations can differ substantially. If the cloud is bound by a static gravitational potential, however, we find strong sensitivity to spurious fluctuations which are induced at the cutoff radius of the potential and amplified by the bow shock. This gives rise to substantial deviations between uniformgrid and AMR runs performed with ENZO, while the mass stripping in NYX simulations of the subcluster is nearly independent of numerical resolution and AMR. Although many factors related to numerics are involved, our study indicates that unsplit solvers with advanced flux limiters help to reduce grid effects and to keep numerical noise under control, which is important for hydrodynamical instabilities and turbulent flows.
 Publication:

Astronomy and Computing
 Pub Date:
 March 2015
 DOI:
 10.1016/j.ascom.2014.11.003
 arXiv:
 arXiv:1411.7275
 Bibcode:
 2015A&C.....9...49S
 Keywords:

 Intracluster medium;
 Hydrodynamics;
 Instabilities;
 Turbulence;
 Adaptive mesh refinement;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 23 pages, 18 figures, accepted for publication by Astronomy and Computing