Neutron star mergers and core-collapse supernovae are some of the most energetic events in the universe, reaching conditions not attainable in terrestrial laboratories. The study of these high energy-density astrophysical events relies on detailed multi-physics multi-scale modeling, ranging from nuclear and neutrino interactions to the large-scale dynamics governed by general relativity. Simulations prove useful in exploring these models, but they are sensitive to the physical approximations and numerical methods used to build them, requiring a balance to be struck between higher computational cost and increasingly detailed physical models. Choices made for the treatment of the neutrinos and the inclusion of general relativistic effects greatly impact the dynamics of how these systems evolve, and impact the nucleosynthesis that occurs during these events. The Flash-X multi-physics code provides an ideal framework for creating the large-scale simulations necessary for studying both core-collapse supernovae and neutron star mergers. This dissertation will detail extending the capabilities in Flash-X with the addition of fully general relativistic solvers for neutrino radiation transport, hydrodynamics, a dynamic spacetime, the supporting infrastructure necessary for coupling them all together, and utilities to facilitate development of these solvers. A multi-group two-moment neutrino radiation transport solver makes use of a novel frequency discretization to improve computational efficiency. A high-order finite-difference scheme is applied to the hydrodynamics. A custom-built code-generator aids in the development of the dynamic spacetime solvers. A new method-of-lines time-discretization in Flash-X provides increased numerical stability and flexibility in choosing time-integration schemes appropriate for both the new and existing solvers. A full suite of rigorous tests validate these capabilities. Continuing work towards the coupled multi-physics multi-scale simulations necessary for neutron star mergers and core-collapse supernovae will be presented.
Read
