[FLASH-USERS] Negative 3T Internal Energies

[Adam Reyes]

Hi Izzy,

Yes that is the typical way to get around that error. You could try larger
values of the cfl, 0.1 is usually a good starting place and would be ~10x
faster than the 0.01 value you're using.

*************************************************************************
Adam Reyes

Code Group Leader, Flash Center for Computational Science
Research Scientist, Dept. of Physics and Astronomy
University of Rochester
River Campus: Bausch and Lomb Hall, 369
500 Wilson Blvd. PO Box 270171, Rochester, NY 14627
Email adam.reyes at rochester.edu
Web https://flash.rochester.edu
 (he / him / his)

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On Wed, Aug 9, 2023 at 7:55 PM Rodger, Izzy <rodger1 at llnl.gov> wrote:

> Good morning!
>
> I'm trying to run the LasSlab example using equation of state tables in
> the sesame format, however an error message that I'm encountering often is:
>
> [hy_uhd_eigenParameters-A]: Zero or imaginary sound speed has obtained!
> Please
>
>  try other (more diffusive) slope limiter, flux, order, cfl, etc.
> The position of this error in the simulation seems to be at different
> points along the target-chamber boundary.
>
> A forum post from 2019 recommended lowering the cfl, and when I did this
> (lowered it from 0.8 to 0.01) I was able to run the simulation and receive
> a reasonable output - but the runtime is very long. I do not receive the
> error when I use the pre-packaged ionmix4 file for aluminium, and it runs
> in a much better time. Perhaps it is a problem with my EOS table?
>
> Does anybody have any ideas for what else I could do to try and resolve
> this issue without sacrificing simulation runtime?
>
> Kind regards,
> Izzy
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