[FLASH-USERS] Problems Simulating Partially Ionized Plasma with USM

[dongwook at flash.uchicago.edu]

Dear Patrick,

As Klaus already have answered to your questions regarding how to work
with ionization, I'd answer your questions about the USM solver.

If you want to look at how species are advanced, please have a look at

  source/physics/Hydro/HydroMain/unsplit/

and you will see the unsplit hydro & mhd solvers. Species advancement
routine is

  hy_uhd_updateSpeciesMassScalar.F90,

which is called from hy_uhd_unsplitUpdate.F90.

But as Klaus mentioned already, if you define species for your simulation,
they are automatically evolved in your simulation.

You may want to look at the full method paper of the USM solver, Lee and
Deane, Volume 228, Issue 4, 1 March 2009, Pages 952–975, JCP,
http://dx.doi.org/10.1016/j.jcp.2008.08.026


Best,
Dongwook

=========================================
Dongwook Lee, Ph.D., Research Scientist
The Flash Center for Computational Science
The University of Chicago
5747 S. Ellis Ave., Room 319
Chicago, IL 60637
(773) 834-6830

> Hey all!
>
> So I am using a little bit modified Flash 3.3 to do simulations on
> galaxy cluster for my master thesis. We have got a MHD setup using USM.
> By now there are two species defined, H and He and the calculations are
> done with the assumption of full ionization. So now my part is to extend
> the simulation that a partially ionized gas can be calculated with
> neutral parts H and He, and ionized parts H+, He+ and He++. After each
> time step the ionization of those particles should be recalculated. My
> plan has been to modify the USM solver. I thought of integrating two
> different densities, one for the neutral and one for the ionized
> particles. Then add source terms to the flow vectors of the USM solver.
> To get those source terms I would have to modify EOS equations.
>
> Even though I did quite some reading about multifluid MHD and spend
> quite some time playing with flash and it's source code I can't get my
> head around some thing:
>
> 1) I recently stumbled over the Ionization module in flash. But I am not
> quite sure if I can use it to do what I want and would not have to
> modify the EOS and USM modules, but change the setup of our simulation.
> This is because of 2)
>
> 2) I read the PhD thesis from Dongwook Lee describing the Unsplit scheme
> for multidimensional MHD and tried to pick apart the USM source code but
> I can't really find out how flash handles (multi) species, density and
> Ionization in the USM solver. Does USM work with the Ionization module?
> If so, can USM handle neutral species and the partially ionized plasma?
> Do I just have to implement the Ionized module in the simulation then?
>
> Thanks a lot in advance,
> Patrick
>
> PS: Sorry if some questions seem stupid but learning flash can be really
> overwhelming!
>