[FLASH-USERS] Stability and timestep issues with 3D Biermann3T Laserslab simulations

[Timothy Mark Johnson]

Hi FLASH users,

I've been trying to do some 3D FLASH MHD simulations of laser ablation focusing on the Biermann battery generated magnetic field. I've run into issues with stability and a very small time step that make the simulations infeasible. As a test example, I took the Laserslab example.par simulation, moved it to 3D, and added Biermann3T. Attached is the .par file that I'm using. For a CFL of .1, the simulation starts out with timesteps of about 1e-19 and crashes (negative 3T) after about a thousand time steps. It also crashes for CFLs of .05 and .025.

Does anyone have advice for dealing with stability issues and small time steps in 3D Biermann3T simulations? I'm hoping to be able to run my simulation for a few nanoseconds.

For the setup command, I've swapped +uhd3t for +usm3t from the Laserslab setup and made the simulation 3D cartesian.

Best,
Tim Johnson
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