Multi-Physics with AstroBEAR 2.0

1. Multi-Physics with AstroBEAR 2.0 Jonathan Carroll-Nellenback University of Rochester

2. Outline • What is AstroBEAR • History of AstroBEAR • MultiPhysics • Thermal Conduction • Viscosity • Resistivity • Self Gravity

3. Actively developed at the University of Rochester • Written primarily using Fortran • Parallelized with MPI • Grid-based AMR with arbitrary sized grids • Conserves mass, momentum, energy and B • Implements various Riemann solvers, and reconstruction methods. • Supports self-gravity, sink particles, resistivity, viscosity, thermal conduction, and various cooling functions. • Integrated trac-wiki system with extensive documentation, ticketing system, blog posts, etc… • http://clover.pas.rochester.edu

4. Originally built on top of BEARCLAW AMR engine • Support for constrained transport, cooling functions, and self-gravity added between 2000 and 2009. • Master-worker model of BEARCLAW engine did not allow for good scaling for AMR beyond 64 cores. • From 2010 to 2011 the AMR engine was redesigned and rebuilt with the goal to scale well out to 10,000’s of cores. • AstroBEAR 2.0 released in 2012 with excellent scaling performance and added support for explicit thermal conduction, resistivity, and viscosity as well as support for more complicated cooling functions and ionization • Ongoing development of implicit solvers for thermal conduction, and subcycling for explicit solvers. • Plans to add cylindrical coordinates, radiation transport, parallel I/O, more complicated EOS’s.

5. AMR Engine redesigned with a peer to peer model for parallelization. It utilized a distributed tree to manage AMR structure, and advance threads to overlap computation with communication.

6. Designed to be easy to use with minimal knowledge of AMR. • Commonly used initial and boundary conditions are easy to generate (clumps, disks, interfaces, outflows, winds density/velocity perturbations with a given power spectra, …) • Many ways to control refinement. • Capable of run-time analysis of AMR data sets to produce histograms, joint pdfs, projections, spectra, totals, various diagnostics, etc… • Also can be used as a highly parallel post processing tool.

7. Thermal Conduction • Official release only supports explicit conduction, though implicit version has been developed and is currently being tested. • Explicit version does not currently sub-cycle, so hydro time step is limited to diffusion time.

8. Magneto-Thermal Instability • Hydrostatic equilibrium with cold material on top of warm material. • Small velocity perturbation. • As field lines bend, heat is able to flow upward, causing material to become buoyant. • As buoyant material moves upward, it amplifies field line perturbations.

9. Heat Transport with Tangled Magnetic Fields • Pressure equilibrium with thermal gradient

10. Conduction Front Test • Self-similar solution for Temperature • Density field frozen

11. RT Instability

12. Viscosity • Official release only supports explicit viscosity. • Explicit version does not currently sub-cycle, so hydro time step is limited to viscous time.

13. Viscosity

14. Resistivity • Official release only supports explicit resistivity. • Explicit version does not currently sub-cycle, so hydro time step is limited to resistive time.

15. Sweet Parker Reconnection

16. MHD Clumps

17. Self Gravity

18. References • http://arxiv.org/pdf/astro-ph/0507212v2.pdf (MTI) • http://arxiv.org/pdf/1110.0817v1.pdf (Tangled Fields) • http://arxiv.org/abs/0801.1403 (Thermal Conduction) • http://arxiv.org/pdf/1201.0754v1.pdf (MHD Viscosity)