RICH: OPEN-SOURCE HYDRODYNAMIC SIMULATION ON A MOVING VORONOI MESH

Abstract

We present here RICH, a state of the art 2D hydrodynamic code based on\nGodunov's method, on an unstructured moving mesh (the acronym stands for Racah\nInstitute Computational Hydrodynamics). This code is largely based on the code\nAREPO. It differs from AREPO in the interpolation and time advancement scheme\nas well as a novel parallelization scheme based on Voronoi tessellation. Using\nour code we study the pros and cons of a moving mesh (in comparison to a static\nmesh). We also compare its accuracy to other codes. Specifically, we show that\nour implementation of external sources and time advancement scheme is more\naccurate and robust than AREPO's, when the mesh is allowed to move. We\nperformed a parameter study of the cell rounding mechanism (Llyod iterations)\nand it effects. We find that in most cases a moving mesh gives better results\nthan a static mesh, but it is not universally true. In the case where matter\nmoves in one way, and a sound wave is traveling in the other way (such that\nrelative to the grid the wave is not moving) a static mesh gives better results\nthan a moving mesh. Moreover, we show that Voronoi based moving mesh schemes\nsuffer from an error, that is resolution independent, due to inconsistencies\nbetween the flux calculation and change in the area of a cell. Our code is\npublicly available as open source and designed in an object oriented, user\nfriendly way that facilitates incorporation of new algorithms and physical\nprocesses.\n