[FLASH-USERS] output question and very low densities issue

[Ji, Suoqing]

Hi Antoine,

Regarding your first question, as far as I’m concerned, there’s no easy way to do so.

For the second question, you can reduce the value of smlrho in your flash.par, which determines the minimum floor value for densities. Since your simulations are in physical units, I suggest you to check related parameters (e.g., smalle, smallt, smallp) as well to make sure their values are appropriate.

Best regards,
—
Suoqing Ji
Sherman Fairchild Fellow
TAPIR & Walter Burke Institute for Theoretical Physics
California Institute of Technology
http://www.tapir.caltech.edu/~suoqing

On Sep 18, 2020, at 2:16 AM, Antoine Gintrand <antoine.gintrand at gmail.com<mailto:antoine.gintrand at gmail.com>> wrote:

Dear flash users,

I have two differents problems regarding FLASH,


1) I would like to know if it is possible to ask FLASH (in the par file or somewhere else) to give plot output with less resolution than the check output. The problem is that I need big resolution for my simulation but it becomes difficult to open them and analyse them in Visit and I would like to have output to analyse with less size than the data used for the real calculation.

2) my second problem is that I am simulating two supersonic flows that collide in the interstellar medium (in 2D) where the initial conditions are two flows in opposite directions.

The first fluid 1 in the left is defined with Density = 1.E-24, Velocity = 1.E10, Pressure = 1.E-5
The second fluid 2 in the right is defined with Density = 1.E-24, Velocity = 1.E10, Pressure = 1.E-7

box size = 1.E13 * 1.E13  (all values are in CGS as FLASH convention)

when I begin the simulation I have the following error :

 INFO: Grid_fillGuardCells is ignoring masking.
 [ 09-18-2020  11:02:30.747 ] [mpi_amr_comm_setup]: buffer_dim_send=46871, buffer_dim_recv=46871
 [ 09-18-2020  11:02:30.805 ] WARNING after gc filling: min. unk(DENS_VAR)=0.9999999999999999237005E-24 PE=0 block=1 type=1
 [ 09-18-2020  11:02:30.883 ] WARNING after gc filling: min. unk(DENS_VAR)=0.9999999999999999237005E-24 PE=0 block=2 type=1
 [ 09-18-2020  11:02:30.977 ] WARNING after gc filling: min. unk(DENS_VAR)=0.9999999999999999237005E-24 PE=0 block=3 type=1
 [ 09-18-2020  11:02:30.997 ] WARNING after gc filling: min. unk(DENS_VAR)=0.9999999999999999237005E-24 PE=0 block=4 type=1

I tried to change the initial conditions and it seems that the problem is that I cannot have initial densities below 1.E-10. But I need to simulate densities below these values in an astrophysical context. What can I do to solve this issue ?


Thank you for your help,

Best,

Antoine Gintrand


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