# hedis

hedis is a code, formerly writtin in Fortran 90/95, aimed at simulating accreting processes, based on works of Duschl & Strittmatter^{1}. The main purpose is the balancing of black hole masses and the mass fluxes towards the black hole.

First, for the one-dimensional modeling only the radial dimension was resolved. The azimuthal dimension was thereby assumed to be symmetric and the height-dimension derived from other quantities. In conjunction with the implicit time integration method these assumptions lead to extremely short computation times. This enables, e.g., the creation of catalogues of quasar-populations. Additonally, it can be used in sub-grids of large-box simulations^{2}. A possible application would be for example early accretion processes in large scale simulations during reionization.

Today, hedis 2.0 has been developed and is based on arbitrary curvilinear-orthogonal coordinates. There is indeed still a spatial symmetry in azimuthal direction, however, the angular momentum is conserved. This leads to a system of three conservation equations for mass, radial momentum and angular momentum, which is numerically solved. The program is structured modularely, which simplifies possible extensions without influencing the generic modules^{3}. Furthermore, this enables a wide spectrum of test cases which verify the proficiency of the code.

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**Ref.:**

^{1} Duschl and Strittmatter ADS, 2011

^{2} Blank and Duschl ADS, 2016

^{3} Illenseer and Duschl ADS, 2015