[FLASH-USERS] Suspected EOS issue in Biermann battery source implementation

[Benjamin Khiar]

Hello Benjamin,

Yes, we are aware of this bug and will release a patch very soon to correct
this issue. Thank you !

Best,

Ben.

Le ven. 6 sept. 2019 à 11:13, Benjamin Spiers <
benjamin.spiers at physics.ox.ac.uk> a écrit :

> Hi All,
>
>
>
> I have recently been trying to use the source term implementation of the
> Biermann battery in LaserSlab-like simulations in order to study magnetic
> field generation in long-pulse laser interactions.
>
>
>
> I found that with laser powers of 450GW I ran into issues with the
> timestep in my simulations becoming impractically small (<1fs), which I
> believe to be because the ions in these simulations reached temperatures of
> 10-100MeV, and so had enormous associated sound speeds. I also found that
> this issue still arose when I added a multiplicative factor to all updates
> to U(*_VAR,…) quantities in hy_uhd_biermannSource.F90, even when said
> factor was set to zero (disabling the source terms altogether). However,
> setting hy_useBiermann = .false. stopped the issue.
>
>
>
> I believe that the issue is caused by the calls to
> `Eos_wrapped(MODE_DENS_EI, blkLimits, blockID)` at the start and end of the
> main loop in this file. This EOS mode doesn’t properly perform a 3T update,
> and somehow flip-flopping between EOS modes like this seems to cause
> significant artificial heating of plasma ions. Switching to
> MODE_DENS_EI_GATHER seems to have fixed the issue for me: magnetic fields
> are generated as expected and the plasma remains at a sensible temperature
> with sensibly-sized time-steps throughout.
>
>
>
> I believe what is required to solve this issue is to change the two cases
> of MODE_DENS_EI to the corresponding _GATHER mode, and also to move the #ifdef
> FLASH_UHD_3T from the next line to encompass the whole loop, so as to
> protect 1T simulations from the inverse issue (It already disables field
> generation in the 1T case so this shouldn’t be a regression).
>
>
>
> Best wishes,
>
>
>
> Ben
>


-- 
Benjamin Khiar
Postdoctoral researcher
FLASH Center for Computational Science
University of Chicago
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