[FLASH-USERS] [Hydro]: Computed dt is not positive! Aborting!

[Ryan Farber]

Hi Jianzhao,

As Benjamin indicated, it would be helpful to know more about your
simulation. I don't know much about laser simulations so maybe someone else
can chime in.

If you were doing standard MHD I would recommend the approach in this paper:
https://www.sciencedirect.com/science/article/pii/S0021999102970099

However, I'm not certain it will be helpful for your case.

You can also brute force an Alfven speed limit by limiting the magnetic
field strength in cells exceeding the limit imposed. However, make sure to
limit the magnitude of the magnetic field vector and maintain the direction
to maintain a divergence-free magnetic field. Even then, I'm not positive
this is safe. You can try setting the limit several times higher to see if
it affects the results (test convergence).

Best,
--------
Ryan


On Sun, Aug 18, 2019 at 10:34 PM 王荐钊 <astrowjz at mail.bnu.edu.cn> wrote:

> Hi Ryan,
>
> Thanks for your reply, I think you are right, but how to make the magnetic
> field smaller? Simulation parameters like laser energy that can’t not be
> changed, otherwise it will not correspond to the experiment. Do we have any
> ways to limit the magnetic field?
>
> ————————————————————
>
> Best Wishes,
> Jianzhao Wang
>
> Department of Astronomy, Beijing Normal University
> No.19, Xinjiekouwai Street, Haidian District, Beijing, 100875
>
> Tel: +86 13141149966
> Email:astrowjz at mail.bnu.edu.cn <astrowjz at mail.bnu.edu.cn>
>           astrowjz at 163.com
>
>
>
> On Aug 19, 2019, at 12:42, Ryan Farber <rjfarber at umich.edu> wrote:
>
> culprit
>
>
>
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