Abstract
Astrophysical disks, such as accretion disks, play a crucial role in various astrophysical phenomena and are of great importance in understanding the formation and evolution of celestial objects. Mass accretion within these disks occurs through angular momentum transport, which fundamentally arises from magnetic instabilities which can be treated with an effective viscosity. Understanding the viscous evolution of gaseous disks is crucial for investigating the evolution of astrophysical systems like white dwarf mergers. In this study, we focus on the post-merger accretion disk resulting from the merger of two white dwarfs, a primary progenitor channel for Type Ia supernovae. The differential rotation of the remnant gives rise to a fluid instability known as magnetorotational instability, which plays a key role in turbulence and angular momentum transport within the disk. To investigate the accuracy and limitations of angular momentum transport in the post-merger accretion disk, we employ a test based on a rotating Keplerian system, treating the disk as a ring of viscous fluid. Our simulations utilize FLASH, a parallel adaptive mesh refinement code featuring a higher-order Godunov hydrodynamics solver. The inclusion of hydrodynamical accuracy in a cylindrical geometry is essential for accurately simulating the remnant’s behavior over a viscous evolutionary timescale. To ensure the stability of our numerical simulations, we enforce a combination of the viscous and Courant-Friedrichs-Lewy time step criteria. The long-term aim is to shed light on the mechanisms governing the angular momentum transport and turbulent evolution within the post-merger accretion disk, thus providing valuable insights into the complex nature of astrophysical disks.