The next seminar “Modelling of materials – theory, model reduction and efficient numerical methods” will take place next **Monday (December 3, 2018) in K3 from 9:00 till 10:30**. The talk will be given by Ondřej Pejcha. Please see the details below.

Speaker: **Ondřej Pejcha**

Title: **Catastrophic interactions of binary stars and the associated transients**

Abstract:

In this project, we plan to employ two numerical methods not commonly used in this subfield of astronomy. First, we will use low-Mach number (magneto)-hydrodynamics, which filters out sound waves in order to not be limited by the CFL condition. We will need to include realistic equation of state, energy transport by radiative diffusion, cylindrical or custom coordinates to capture non-spherical objects, complicated boundary conditions (stellar surface and excised cores of the stars), and eventually magnetic fields. Small regions of the domain might become supersonic. On the other hand, we will likely not need adaptive mesh refinement, nuclear burning or radiation transport beyond simple diffusion/conduction.

Second task aims to build moving-mesh radiation-hydrodynamics in 2D and 3D to study aspherical shock collisions and instabilities. The idea is to combine many essentially 1D Lagrangian spherical cones with transverse fluxes. For radiation, flux-limited diffusion will be sufficient (implicit update to explicit hydrodynamics), but detailed microphysics is important: realistic equation of state, opacities, and potential complications like small chemical reaction networks and growth of dust.